Honestly, I wouldn't mind ML joining the 765 cast. Yes, some of them are pretty bland but I always thought of it as 765 Pro becoming more successful and hiring more idols.
As for CG, I believe they would have their own spin-off title, and only 23 idols have voices right now, I think. Unless Namco wants to throw in surprised voiced idols as incentives lol.
More 876 and Jupiter is a must. I would love to produce Yumeko, Cineria and Reiko. Mai would probably end up as a rival.