Bit late to the party, but loving the game at the moment - must have restarted at least 100 times by now!!
So just a few suggestions if a sequel (or update) is in the works:
1) For the Idol auditions, attendees' ranks (or at least stats) should be based on how good your company is (or doing). Why would platinum idols want to join a non-reputable upstart company when they could potentially join a more successful competitor? I say this, because sometimes you could get 3 superstars right from the start, and this greatly affects how the early game is played - I think this makes them miss out on how the developers intended players would approach the game.
2) Having the producer/manager (me) be the only person to perform certain jobs really bottle-neck the production process. Having a nobody (or even a regular manager) be in charge of writing lyrics which could potentially make or break the entire company would be in most cases absurd in real-life! Perhaps they could outsource or have permaneant staff to do the job. If an idol has enough experience singing (centering or 2nd row) with a group or they reach a certain level with their vocalist skill, maybe they could be able to submit potential lyrics to the producer - an option regardless of whether they are accepted or not.
3) Also, for mods - instead of parameters like "unique" and the "can_be_hired_again" - make it an option in the settings so players have the choice as a mixture of modders and their decisions can lead to some implementing them and others not...
Been 3 years since the intial post was made and quite a few days since the last post - hope this gets heard (visually, of course!).
Thanks for a fun game!