Ok so... my game does not start after the lattest update. It just shows the cover art forever after I choose the MC's and group's name.

but other than that, here goes some suggestions I have after playing the game for months now:

ALBUMS and Music Videos (c'mon, everyone wants this simply because it can't be a music industry sim game without it, so I'm just going to lay down some must-have features for this)

The MC should be able to write all or just some of the songs for the album or hire a team of producers to do it partially or completely. The MC must be able to choose from unknown writers/producers to worldwide famous teams which would determine both the quality and budget of the project. 

The MC should be able to decide how long the album takes to be finished and that will also affect its quality. 
During the album production period, many random events should take place and they can also affect the album quality or even increase the amount of time the project takes to be finished resulting in the delay of the release.
Like, 'idol-A' fights with 'idol-B' over line distribution or 'idol showing late for recording' or 'idol is sick and can't record' or even songs leaking online. 

Also, albums should have a cooldown period and the possibility to release Repackaged (re-release) albums with a new title track and a couple of new songs. 

Fans should demand albums to be released if they feel like it has been too long since the groups latest comeback and if that happens, you would have to work a project with a deadline, suffering the loss of fans or sales impact if the album gets postponed by random events.

MC should be able to decide whether the project is a full-length album (10-15 tracks), a mini-album (4-6 tracks), a Remix album (10-15 tracks), or a Greatest Hits album (up to 25 tracks). 

It should also be possible to use unreleased songs and singles that weren't on past albums on an album currently in development (that would help if you're short on money for the production or simply want to save some).

Once the album is ready, it should be possible to send it back to production if you don't like the end result (quality) at the cost of idols mental and physical stamina. This is also a cool feature because if the quality is low because of fights between the idols or idols being irresponsible during the production period, that could even generate more drama between the members and if it gets really bad, the quality may even be lower than the first time urging the player to solve the situation as fast as they can. 

The player should be able to release up to 3 singles from each album and all 3 can have their own music video. 

During album production, the MC should be able to buy songs from other artists/companies to complete the album faster. 
The MC can also be approached by famous or washed up music producers claiming they have the next #1 smash hit and they want to sell it to the company on the condition that the song is released as one of the singles from the groups next album. Those would be contract singles that can randomly do well or not so much in the charts, they could generate random events both negative or positive such as plagiarism claims or subliminal messages in the lyrics or be deemed Genius Lyrics or Song of The Year. Nonetheless, the player can't proceed to another album or single production before releasing the contracted single as the 1st, 2nd, or 3rd single from the current album. These songs would also be sold for really cheap prices in comparison with the ones the player can buy ready but would have a much higher royalty % for the original producer. 

Music Video production can be easy, you just have to pick the theme, the budget, director and production company and location for the shoot which can be in any country affecting the budget for the video. Random events should also be connected to the MVs production.

Companies and Brands should offer sponsor deals related to music videos so they can pay for half of the production budget in exchange for having their products promoted on the MV.

ABOUT RANDOM EVENTS: 

Then again, not all random events in this should be negative. We can have some things like, 'idol-A' really improved her vocal skills and that showed in the latest recording session. Album gets x.x% bonus quality points.' or for MVs 'idol-B showed up for shooting with a very nice energy that affected all members and the crew. MV gets x.x% bonus quality points' or even 'idol-C showcased her dancing skills during the shooting resulting in amazing takes from the dance scene. x.x% bonus quality points'.
Even though that, more serious negative events not related to idols relationships could also take place like 'during the shoot of a stunt scene, idol-c injured her leg, shooting had to be postphoned. -x% quality for MV.

EXTRA FEATURE: (since I know this is based on the Japanese Idol Industry, I'm not sure if this one really applies but, anyway I just think it would be a nice feature)

Idols may develop artistic traits and work on original music, the player then would decide if they are using it or not. Maybe idols with artistic traits could have WISHES of having one or more self-composed songs on albums. The Idol's original songs could have their quality based on their abilities so if you think the songs isn't good enough, you can politely tell the idol she should work harder and that can have a negative or positive turn out in your relationship with the idol depending on the idol's personality traits. 
If the idol's song is good but doesn't fit the concept you're going for or you just don't want to share royalties with them you can refuse to use the songs also at a risk of impacting the relationship with the idol or only inciting them to want to end their contracts earlier because of lack of creative freedom.

Wouldn't be great if we had random questions like moral dilemma like: "if you use sexy concept there is 20% of chance for your song to become viral (and sell 1M copies even if you're a nugu) but there is 80% of chance to lose 50% of your fanbase if the song doesn't go viral, what would you like to do?"

Ofc after the song goes viral or if it goes viral, our next single can still have nugu sales because people were only interested in a viral hit and not our other song.

That would be pretty cool. It would be more risk and more consequence. There should be a lot of such questions during the game so we wouldn't get the same scenarios like now over and over again.

I have a suggestion for the graduation system.

 1. I would really love to be able to keep my Idols longer. All of the idols graduate usually at a young age like 18 or 20 years old. It would be amazing for them to still be an idol all the way up to age 30-35. I don't really like how I have to keep finding other idols by doing auditions just so I can replace my graduated idol.

2. Instead of having a set graduation date (they should always graduate/retire if they reach 30-35 years), it should be the idol's choice to graduate or not until they reach the max age. Idols could graduate if they decide to stop being an idol (could depend on mental stamina if it gets too low or they are involved in a lot of scandals, being bullied for too long, etc.). They could also leave because of a personal reason (maybe their family member died, if they are young and still in school; they can leave to continue studying, etc.). 

3. If the above suggestions are suggested, it could also be added that idols can return (if accepted or declined by the player) back into the group if they graduated early before the max age.  For example, a idol could've graduated to continue studying but decided to continue being an idol instead.

4. Would also like to add the idea of trainees. Trainees can be trained until the player decides to debut them. It would add a more realistic feel to the game. I think it would be awesome if we could list 12-16 year old idols as trainees and be able to debut them at 18 or so with their updated attributes.

Hope you take these suggestions into consideration. Most of all, I really hope you can adjust the graduation ages to be higher instead of the normal 19 or 20 age.

I have some suggestions related to user experience.

1. Automation for sociable and activities. 
Sociable. When I intend to improve influence I have to drag and drop each times. It is a little bit irritating. So I prefer to choose persons whom I intend to do sociable, and automatically assign them to sociable tasks.
Activities. I suppose there is no need to select activities each days, I prefer to select at once. And repeat same activities every day automatically.
2. Pause functioning
When I unpausing the game by space-key game speed returns to normal. I suppose it might be better to return to speed previously selected.
For example, 
current double-＞pause-＞unpause-＞normal
suggestion double-＞pause-＞unpause-＞double

It would be great if when you hover over the number of fans, you can see which sister groups have how many fans.

I'm not sure if this thread is still being checked but in the future could the devs consider adding the ability to buyout other companies/labels? Like if you keep outselling/sabotaging a rival group, the stock prices of their company should decrease overtime and if the player has enough money (or if they've bought small amounts of stocks overtime) they could buyout their stocks and merge the company gaining all of their idols, staff and remaining fans or just have the company as a sub-label that generates income if the player maintains it. There could be a menu where the player could decide which idols or staff member to transfer between the sub-label and main label. Also there could be random events like natural events or economic crashes that could also affect other companies' stock prices. 

Another idea i have is the ability to open your own training academy. I find it annoying to have my popular and well trained idols graduate and then i have to replace them with idols that aren't as skilled. So there could be an option to open an "idol school" that basically would "farm" future idols. For example the player could hire specific vocal and dance coaches (or graduated idols) to train young idols for 2-3 years. The player could make money by setting the training price for young girls to enter and after they graduate from the academy the player could have the option to let them join their group or accept a large sum of money from them. It would be cool to see the rejected girls appear in rival groups or have events of them harrassing the player's pre-exsisting idols out of jealousy. The player could even accept contracts from larger rival companies to train their idols at their academy for a hefty price (if the player graduates a specific amount of idols or something). 

Thank you for working on the game devs, it's a really fun game and i look forward to seeing how the final product turns out! <3

I also suggest what we should get gold idols when we do local auditions because let's be real after talented trainees leave from very good companies they also end up in small shitty companies or talented idols were rejected from big companies for whatever reason for example we could get gold idol with great vocals and dancing skills but they would not be cool or pretty because for example this is why they ended up here, others didn't want them because they were ugly by idol standards. It can be very small % to get them like maybe 0.2% but it would be nice if we could get some talented gold idols in local auditions.

So first of all, I want to say that I've been enjoying the game immensely, even though I've only been playing for a few days so far. I don't know how deep the existing content goes, so I apologize if some of these are already implemented or planned.

The first one is something that I'd consider to be a rather big QoL improvement; the other two are just things I think would be nice to have.

1. Show the relationship meters in the Socialization screen. Unless I'm missing something, there's no way to actually check your relationship stats while you're actually in conversation. It would be great if, for instance, you could see an idol's Influence value before you try to blackmail her into doing something for you. I generally try to double-check their profiles before I enter a conversation, but every now and again I forget to, or else I need a refresher.
2. Right now it doesn't seem like there's much point to keeping on an idol as a staffer after she graduates, as there's nothing really differentiating her from Generic Office Temp #4021 other than the unique portrait. It would be nice to have something like a unique stat bonus, or else some minor post-graduation events that pop up occasionally based on the relationship you developed with her while she was still active.
3. Personalities that evolve as an idol ages. Not necessarily asking for something like a full-blown Crusader Kings-style trait system, but it would be fun if each idol had a small random chance of gaining a second trait on her birthday in addition to the one she starts with.
   

I've been playing the game since may, and I must admit that I love it.

But as I was playing, I was thinking that I could be very amazing to not be imposed groups of ten. As I know it could disbalance the game to have smaller groups, I was thinking that the amount of smaller groups could be restrain to a certain amounts, per fame of you company maybe ? I don't know yet, but I think it would ba awesome to have the ability to create duos or trios without having like 30 idols in your main group in order to do so.

I also was thinking that saving the formation you did would really help, cuz when you start building up a big company it is easy to get lost in your idols.

And also, I know you can see idols according to your sister groups, but it would be really nice if we could (when you do a single with your main group) have an option to only see your main group (or at least have them all put together and not having to scroll your idols for them (who would be in between the members of two differents sister groups)

Since the upcoming update can   influence  idols to stay with the group longer. I hope I can convince famous graduated member to join anniversary or special single.

and I also hope there is b-side or coupling song that can choose member to participate too. [ Just like main single but you can choose member for coupling song too ]

Another one to add to the list:  It would be quite helpful if we had some sort of ledger / account book where all of the financial info is gathered into one place for easy review, broken down by month. Right now it seems as though I have to hunt around between several different screens to find it, and I don't think revenue for singles and concerts is logged anywhere beyond the individual results screens for each one.

I was thinking, maybe a room, appart from the theater, that can help to rise the smart and funny of your Idol might be something quite interesting. Like classrooms with teachers in humour or smart things, I don't know at all, but since they're calculated on the percentage of success of the new promotions, it would be quite nice to do do something with it

If possible at this point, some Nogizaka references would be nice. Seems like everything I see is AKB/Keyakizaka.