After reading through parousie's ideas, they hit on two things I'm interested in as well: Recurrency/continuous single sales. As is you release the single, and whatever it sells first week is its "total lifetime sales". I'm also interested in seeing singles continue to sell beyond their release week like actual singles in their example. It'd be an extra source of income, and could add some more decision making: Maybe an old single might sell more when its genre/dance/lyric style is trending? Maybe new genres and marketing styles could be introduced that improve longevity of single sales, or trade-off debut sales for increased sales over time. Could make copy production more involved too: You produce 300000 copies of a single, take a bit of a loss and sell 215000 singles 1st week, BUT those 85000 leftover copies can be bought over time, and you'll continue to see sales if your single had the right genre/marketing choices. On the other hand you might lowball how many copies you needed, and sell all 300000 the first week or very early on, now you can't take advantage of your song exceeding expectations and possibly selling another 50000 copies in the next few weeks, had you made that many.
Also agreed on how the game does sorta encourage you to only work with platinum idols (The new awards benefit for Best Employer pretty much ensure you'll mostly get silver/gold/plat idols), when normal ones mostly build the foundation for your company, and are the ones you attach to first and most strongly. Your highest earners and first centers are most likely normal idols, but they're objectively worse than most idols you'll draw after your first in-game year. I wish there was A) a way to disable special idols and B) following that, a way to rebalance regular idols to have strengths somewhat level to the special ones.