Hmm, I prefer more in-deepth relationships with already existing characters rather than more characters romance. Not that I'm against more NPCs, I actually love the idea of filling the world with more characters (store owners, people doing exercise or just going through their day), but not every character needs to be romanceable (maybe a lewd scene or two).
I like all of the phone ideas, you can even unlock some quests by looking at the students gossip and such. Same goes for navigation and the gameplay, they are good as is, I like minigames as long as they give some smallish rewards for trying to beat them (like RP or stats or even scenes).
I love the idea of hidden scenes, it can be even greater if they are tied to an especific stat check. It does not even need to be a lewd scene, some extra cute, romantic or funny scenes are always welcome.
I liked the relationship system the most and I think you should focus on making the cast have some more meaningful interactions with the MC and each other. I like the idea that you can lose or win some relationship points when you overhear two characters talking about you depending on how you interacted with any given NPC. This makes your choice seem more important.
Apart from all of that, I like the first level of the feminization level a lot (he became so much cuter), but I don't really want the MC to become full female that much. It's fine and I don't care much, but I really like him more as a male/femboy. Can I stop the feminization route after starting it or if I enter it he will just became full female no matter what?