The thing about Mewtwo is that it'd be way too powerful if made closer to canon. A balance would be nicer, but it's forgetting the intent behind it; the moves used, bar Disable at best, make a ton of sense for their purposes. Confusion is a powerful move at the time, and the way it's used heavily fits the anime inspiration. Teleport is a blatant Up B option. Shadow Ball is actually still good too. The tail attacks are a good way to give it reasonable appendage usage that's easy to animate. The elemental attacks show that it's a versatile Pokemon(though this is somewhat more Mew's things, but it was cloned from Mew, so it still works out).
The glass cannon thing isn't that accurate. It doesn't have massive power. By being a floaty character, this means that they're designed to... be knocked around a tad easier. Floating implies a bit of lightness weight-wise, especially since you can't directly grip the ground since you're outright hovering above it. This is actual reasonable game design. Note that those with special jumps don't always float like Mewtwo does, so they have a different defense option in return. Though it can vary(as some still may have lower defense due to having better jumps so they're more balanced out in a platform fighter and all).
Mewtwo does need more power, imo, to counter balance the particular defensive style and floatiness. But beyond that, it's fine. I'm sure Disable could be changed up better, and Confusion not reflecting a projectile is a bit odd(though considering in the anime it was mostly to move said projectile to the side or pick up a character and throw them aside, it's actually very accurate to its design. The fact it is fairly meh at throwing the enemy is where I feel it could be fixed up. The way it handles projectiles is fine, though. It's a good contrast to how it isn't using a regular Reflector nor was intended to).
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As for others, I don't think anyone should be outright redesigned. It misses the point. Now, updated so they work better is fine. Little Mac having a horrific air game is unnecessary. It doesn't need to be awesome either. Sonic is an oddball in that the point behind the two spins were that he was good at being fast and could throw people off their game by having two very similar moves that worked differently. This concept is fine. He's actually a fairly good character anyway. He's literally 2nd in the Ultimate Tier List. It's clear that he doesn't need changes to make him good. The only real thing he could have at most is nerfs, honestly. Steve/Alex is a different mess that has a problematic tech(which did lead to some banning it or the character) that would be nice to remedy for the next game.
Lucario I like the idea, but I do feel it needs more non-aura moves as strong options so it's not Aura or Bust. This also could be a good case for having something like an alternate playstyle(not as an Echo, of course) that would focus on a different way to play. Of course, this is probably never going to happen anyway, so it doesn't matter, heh. That said, my only thought on Ganondorf is his inability to reflect a projectile. That's kind of a major thing that would vastly help him(and he's already at his most viable since Brawl with Ultimate's buffs and unique mixups he now has). Otherwise, Up A is a pretty bleh move in practice(it's kind of okay at edgeguarding, but it has zero super armor, making only Warlock Punch something that at least encompasses his massive power and is actually usable thanks to that super armor).
