I just hope there's a trio performance option at some point XD The thing I missed most from SP (besides the flashing costumes) was the ability to have duos and trios.
It just expands on everything that you can do in the game. Even with just 3 characters to choose from, there's a lot of options for different sounding songs and different looking performances

the only evidence against this is that there hasn't been any duos or trios shown in any of the previews. But, then again, there's probably quite a few gameplay bits we
haven't seen.
It's so hard to say. XD
Oh, and Nanashi-san; there was a different idol-likesomethingoranother for the DS (Kirarin Revolution or...something, I don't remember).
Someone posted a youtube video to the ad while we were still guessing how the stage performances would look XD
I'm sure iM@S has things that the other game didn't, but that game was able to handle 3 people on one stage, so I don't think they'd leave out the feature due to limits.
They'd leave it out to make us buy the 360 game or wait until 2nd Vision console game, maybe...