is to be able to modify your idol group. to modify your idol within the game allows the users to project their idea of idol group to the game even more. At the moment, the current system of Idol-management allows the users to project their ideas about idol groups pretty much, but some are still missing. why aren't we allow to change the outfit of each idol? can we designate fashion concepts to each album?
I think its important to let steam workshop users to mod the hair/outfit/face/pose/general in games, this will make the game mediocre to great.
Also, the game needs to generate some images of in-game idol group by showing the custom outfits that the user selected. user should be able to select outfits and poses for each&group of idols by each single album release, concert, or any media works.
more outfit/poses unlock by research concept with the stylist.
At the moment the game is okay, what the users make playing this game over and over again would be able to project user's own ideas about idol group.
just make sure don't forget about idol customizations. stories and events are second thing. remember how other mobile game companies make money by selling customization images in-game. not that you should pull money from the users, but you should understand that is what real users desire.