Forgive me if it's simply a cultural thing (I'm not overly versed in idol culture) but it sorta feels like we're forced to play in a certain way. You're rewarded for convolution and having 20 idols rather than say, having a core group of 3-5 that you want to take all the way to the top. I noticed that when I released singles, the quality of the single went up the more idols were in it as opposed to the quality of the idols that were in it which doesn't seem quite right imo. I think it'd be nice to support different playstyles, like having small units or solo singers with individual act names. You might still end up with the same quantity of idols, but not in the same group.
I also think it'd good to be able to retire songs from concerts. You always end up with a million singles so when you go to plan a concert there's always a super long list of songs, many you will never touch because old/low quality.