Hello,
Some suggestions :
- Add idol graduation date in their profile, when you have a lot of idol it's hard to remember
- Add possibility to filter songs when selecting song for a concert
- Add possibility to sort singles by date, fan satisfaction etc
Adding to #1, it'd be nice if graduated idols were moved to some sort of "hall of fame" where you could view their profiles, or something along these lines. As a bonus, this could open up a possibility to (still) interact with them in some manner.
Also, maybe an option to set a concert as a "graduation ceremony" for an idol that's about to leave soon? It could make the fan base of that particular idol more likely to attend, or smth.