... Ya know, there's just been this thing in the back of my mind during all this...
When game 1 is a hit, a safe bet for game 2 is more of the same, with some modifications, and if keeping the same characters, they're developed more. Like, Im@s2 with 765 + former 961 (+ 876 maybe), but the promo events are all more character oriented. Like, being able to interact with Yayoi's siblings (with CVs for them), talking with Azusa's mom, or... hiding from Yukiho's dad. You could even toss in, like, two promo events where one of your idols interacts with another you're producing (or not producing) at the time. Change the auditions and lessons to keep things fresh if you want, give everyone a new look if you want, but you don't really need to go as far as they seem to be going. Im@sSP with 961 idols and your option of duos or trios with more personal communications would honestly have been fine... I think (^^;). When you get right down to it, all the people who wanted to produce someone from Ryuuguu in an improved Im@s... are now left wondering whether they'll ever get that game.
When you get to the third game in the series, that's the point I think you need to change, or stay forever the same. This could mean a new cast, or just radically new gameplay changes. Or, radical changes of any type, like what we're seeing here.
... Just something I've been pondering. I dunno, really... I'll be honest when I say they're just random thoughts.