The funny thing is that Mewtwo looks like its using some moves from Melee, but fixed to have a stronger presence or work better like how multi-hit moves in this game link much better for the most part... Zelda's Up and Side Smash and Falco's Up Smash which I think has the only issue of the knockback on the first hit which shouldn't be there or should be toned down as Utilt doesn't have base knockback and only growth on the first hit, but I digress.
One thing: how would Wolf work now because of Falco having his Bair? If Wolf takes Melee Fox and Falco; and Brawl Falco's Bair, then that's a literal kick in the face to Falco who loses a sex kick that could help him in disadvantage while Wolf gains a sex kick to complement a good Nair. There was even
an old image showing Falco in a similar pose to his Melee and Brawl Bair or it could be the first few frames of air dodge - probably not - or the current Bair. Giving Falco's Bair back would be a patch of its own. Well, there's my Falco spiel.
Onto Wolf, voice. Would Wolf keep his Brawl voice or follow the theme of Star Fox 64? That would be a bit weird since it just doesn't fit his appearance, personally. If he goes 64, then Wolf might actually have a new model which once again, would be weird since it'd be only for this game and then SSB5 and Star Fox Wii U might have Wolf looking different. This wouldn't be like Link staying in his Twilight Princess outfit which is similar enough to Skyward Sword and to many, it's the "modern" Link outfit. Wolf didn't have an outfit like Fox and Falco that stayed consistent barring two games, Adventures which he never appeared in, and Assault where he has his current look mixed with Star Fox 2 concepts. Y'know, it might be better if Wolf gains a new model based no on 64 or Assault/Command/Brawl, but on the upcoming Star Fox game just to tease it.
Speaking of which, I feel like Wolf might be kept as a tease at the end of a Star Fox Wii U trailer sort of like how Capcom teased Vergil and DMC4: Special Edition in the DmC: Definitive Edition announcement trailer. When DMC4: SE got a gameplay trailer, not only Vergil was shown playable, but Trish and Lady too. That little tease built a ton of hype and while DmC and DMC are in different situations, could you imagine the hype with a little tease at the end of a Star Fox Wii U trailer? All it needs is Wolf saying, "Can't let you do that, Star Fox!" and a tag saying Wolf will join SSB4 at whatever date. They could have Wolf be a pre-order bonus, a code that's part first print copies which hopefully won't get scalped, or just standalone and part of Star Fox Wii U's launch.
With customs, I remember talking about it, but it's a bit more interesting as Lucas kept his PK Freeze. What if there were property changes to make Lucas's PK Freeze different to Ness's PK Freeze custom sort of like how by default, their PK Fires were different. Lucas being able to kill with PK Freeze would be great alongside maybe a quicker setup time and freezing longer and earlier. Or the chance that Wolf Flash just gets transferred over and Fox gets a replacement customs which would be cool as Fox gets a new custom, but it's still interesting to see how Fox uses it and that Fox gains a spike alongside Fair spiking which is difficult from what I've seen.
I really, really want Wolf in the game. The hype is affecting all of us.