U might've already read these but:
https://www.mangago.zone/read-manga/saving_the_doomed_idols_with_my_touch/
https://www.mangago.zone/read-manga/meteor_orbit/ (this one's a bl and the mc regresses rather than being reincarnated as an idol but he has a system)
https://www.mangago.zone/read-manga/monochrome_rumor/ (also bl but it's v v slow burn so it's almost non-existent, no system in this one)
THANK YOUUU. ive been looking for the 3rd one
Maybe this count? "I, Who Used to Be an Idiot, Was Possessed by an Idol?!"
PLEASE PLEASE