Hey there, I love Bemani games: IIDX/PNM fan all the way! I am also a lover of most things that came from the Q-Sound era (Capcom).
I am excited about the possibilities of reactive music games, though. I think there is a lot of room to explore there.
As for rhythm platforming: this may not be the like Galaxy but, I found this cute flash game that immediately came to mind:
http://www.kongregate.com/games/Coolio_Niato/music-in-motion
**All that said: I am asking the community if they know of any games other than VIB RIBBON, beat hazard, and audiosurf that uses people's mp3s to make music. I've searched bemanistyle.com's forums for game ideas, didn't come up with much. Maybe you all also know some good websites or forums to lurch around??**
Sorry I wasn't clear.