Ha, I voted Yuni into Smash. In some happy universe, it'd be grand if she could bring in like the SN2 stage from Wreck-it-Ralph into Smash bros. It'd be even more grand if her alternate "costumes" were the other characters.
Mm, fast DDR stuff would suit the Star Fox and Megaman stages well, I think. Maybe something for the 3DS Pac Man place. They're pretty groovy stages. Ska a go go would be fun. But yeah, your guesses are better than mine; too much Bemani music to think about the ones outside my favorites. @_@ Sumidagawa Karenka for the new Street Fighter one, Resurrection for Miiverse... I wonder which parts would get cut if they had to be on loop for a Smash stage. Maybe not much; they're all already short enough.
Snake would be neat to come back. I only care 'cause he was one of the heroes in Subspace Emissary and I like seeing them all together. Last I heard, it was Mr. Kojima who requested Snake in Smash rather than the other way around, and with him out of Konami it'll be one awkward reunion. Then again, Mega Man's original creator lost most right to his own character and MM was in Smash... anything can happen, it seems. Woo hoo?