I hate Mii costumes, but I'd love the Frieza battle suits. Imagine the meme material, like Mii-Nappa.
In all honesty, despite how much some people hate the idea, I wouldn't mind if pre-DBZ Goku made it into Ultimate (
NOT Kid Goku). His moveset could implement the Power Pole, and he could just use the Kamehameha for his final smash instead of going Super Saiyan. This way, you could use the version that everybody recognizes (just from a different time in the show), while still staying true to the character. Super Saiyan Goku would be too over-powered for Smash, and his form wouldn't fit in with the new final smashes (he'd basically be another Super Sonic).
Say "b-b-but he originated from ANIME" all you want. I personally can't stand anime characters (well,
modern anime characters) the most here, but Goku just works and makes sense. He's not some stupid femboy like most male anime characters these days (although his Japanese VA is female). He's iconic, and aside from Dragon Ball, he represents a whole entire sub-genre of fighting games. Dragon Ball has also had titles on Nintendo consoles since the
FAMICOM (he's even on the front side of the box of a special edition gold Famicom Mini releasing in Japan). Sure, it'd break the whole "only video game characters in Smash" thing, but since when has that been a strict rule? Sakurai has been known to change his mind, and let's not forget,
James ****ing Bond was planned to be a character for Smash 64 (and possibly even Melee). Goku would fit in way better alongside characters like Mario and Cloud, and his inclusion wouldn't mean he'd open the gates for more anime characters (like people keep suggesting), he'd simply be a "single strike of lightning" deal, kinda like how people viewed Cloud when he was originally announced.
And last but not least, Sean Schemmel's beautiful voice in a Smash game. We could even get his King Kai voice for Snake Codec-style telepathy conversations.