I don't really hate Jupiter as much, but none of them are Ryou... So no 876 idols yet? I mean with this game's focus on idol groups rather than the individual idols, I would think you could use those three as even more competition storyline-wise.
Aside from the general unpopularity of iM@S DS, I'm a bit surprised they haven't showed up, myself. Of course, they -are- from a different agency...and we probably can't be double-agent Producers. XD (that, and we're already running against RK and Jupiter)
However, for a game that was focused solely on those 3, never getting to see them actually perform as a trio (or in HD graphics) is disappointing.
Maybe they'll get a cameo?