While I have no interest in playing Sequence, I like the combination of notions: an RPG using DDR as its combat mechanic. What mechanic you use to represent conflict in your game is essentially arbitrary. We already have several Puzzle Quest-like games where fights are won by something like Bejeweled. It’s all a mini-game anyway, so if you like rhythm games, here is one where you use it to vanquish your foes.
Where is the anime-style game using karaoke mechanics to let you defeat your opponents through the power of song? Giant robots and singing have been merged so successfully on the screen, why not on the PlayStation?