Hi, fate here. I actually noticed something interesting in the game recently. It's that each character has a specific change in accessories and/or clothing through each individual route, and they don't seem to last very long, even considering they look well made. I've only played Mika and Julie's route, though I don't doubt there is something in it for Nemu and Mariya.
Considering these are exclusive for specific characters and seen only sometimes, how about we add an economy-based mini-system? Now hear me out: Why not get "points" for actions such as making choices or finishing a route. The main menu could have a tab called "clothing store" unlocked and you'll be able to buy Miraya's waitress outfit, Blacksong outfit (Mika), Hair dye (Julie), and so on. On purchase, the original files would just be replaced by the special outfit ones, and you'll be able to see the character in new clothing/accessories when you play the game through another time.
It's a random idea I had and I expect you not to take this seriously, though it's pretty simple and you guys have nothing to lose so i thought about posting it. Hope it helps!