Dragon Quest would be nice, but I can't imagine being that interested in most of the old scores unless they were the orchestrated versions of the music. I still have some of the old orchestrated OSTs; they're very nice>
For all of it's faults, Chrono Cross did have some amazing music even beyond Time's Scar. I'd be interested in a game that covered a lot of Square's other stuff like Vagrant Story, Xenogears or Valkyrie Profile. None of these were on a Nintendo system, of course.
I kind of wish the new Theatrhythm covered more Final Fantasy Tactics tracks; I'm happy for the few that are appearing on it, though.