Hi, thanks for the positive feedback! I'm a solo dev and I have one sprite artist at the moment, so each addition to the roster is a big undertaking. Compared to Koikatsu there's thousands of custom lines that needs to be written and tens of events. That's why I'm mainly focusing on my own picks as I otherwise run the risk of losing motivation or the game falling in quality. But I do hold polls on Patreon where you can help decide some of the picks, so the fanbase is taken into consideration. Whoever wins the finals in those are added to the game.
In terms of the schedule, with the current setup it's not set in stone where a girl is at any time, they just have set possible locations. It's mainly to keep players from chasing one girl too much, turning it into a "go here at x time to gain affinity" kind of a thing, and encouraging variety. There's pros and cons with this of course, but I'd rather do this as a starting point and be able to plan specific dates or meetings with girls manually, which are more rewarding. Or, once weekend gameplay is added, ask what they're doing for the weekend and you can find out if they'll be in the city, the countryside or at the beach so you can plan accordingly.
Oh, and if you haven't experienced any heart events yet (the ones that increase heart level) I hope you do :)