While I beat Final Fantasy 7 for the first time earlier this year, I'm not overly familiar with specific songs in that game, so I'm interested to see what music we get beyond some form of One Winged Angel (whether it's the original version, the Advent Children version, or something else). ...Unless it winds up being like Cloud in Smash 4, and we just get One-Winged Angel and One-Winged Angel (Advent Children Edition).
Hopefully we get songs from other Final Fantasy games beyond 7 as well, even if they're just added through Mii costumes.
Dancing Mad, or at least one of the four phases, would be amazing, and while I haven't played Final Fantasy V,
Battle on the Big Bridge gets talked about a lot, and it sounds like it'd make for a great addition.