Yes, I suppose that would be an interesting game. I mean, she proved she can handle villians and monsters in SMRPG, so why can't she do that again, only, alone. But, if Nintendo were to make that game soon, people would think they were copying FFX-2 (Only girls in that game, for those of you who don't know). Nevertheless, I don't see why Peach can't star in her own game.
Made you look.