Well, given that I've already got Mewtwo, I'd absolutely love to see Dragalge join the tourney. He's just so cool-looking and well-designed, in my opinion, and I think he'd be awesome in Pokkén Tournament. He could use a mixture of weak, long-ranged, continuous damage-inflicting attacks, referencing his Poison-typing; and flashy, powerful, close-ranged attacks, referencing his Dragon-typing. That way, he could pressure the opponent into approaching by using his Poison-type attacks, and then wallop them with his Dragon-type attacks once they close in. He'd probably have to have a crippling weakness, like being really slow or having exceptionally poor HP, to balance that out, however. I'm personally alright with that, though. Plus, Dragalge would look glorious in HD.
Besides Dragalge, I think Cofagrigus could be interesting, too, given his multi-armed physiology and levitating abilities. Cofagrigus isn't necessarily one of my favorite Pokémon, but his design is nice, and I think he definitely has potential in Pokkén Tournament. A snake-like Pokémon would be interesting, as well, and, while I don't have a preference, I'd personally choose either Seviper or Serperior. They're the coolest snake-esque Pokémon, in my opinion, especially Serperior, since he, along with Dratini and Dragonair, breaks the trend of snake Pokémon being evil-ish Poison-types. Oh, and Bidoof, just for the mountains of salt that would surely follow

.
Actually sorta serious...
I know this post is probably starting to drag, and I apologize, but I just have to get this last thing out of my system. So, all of the talk about a third Mewtwo Mega Evolution and an MMX-MMY fusion got me thinking, and I thought up a hypothetical "Mega Mewtwo Z" that I tried to design as an amplification of Mewtwo as a whole, rather than an exaggeration of individual traits, like Mega Mewtwo X and Y did. I've always been under the impression that Mewtwo is a heavily offensive Pokémon, so here goes...
Little iffy on it, since I'm no competitive Pokémon expert, especially on his typing. I felt like, since Mega Mewtwo Y was pure Psychic-type, Mega Mewtwo Z needed a secondary typing of some kind, and Fairy made the most sense to me, strangely. I dunno. I guess it's just something about Mewtwo's design. Anyways, any thoughts or feedback would be greatly appreciated, especially from
ZephyrZ
, since you influenced the design philosophy I (tried) to follow.
Also, new Christmas-themed avatar featuring Mew, Mewtwo, and Ambertwo! :3 Wee-hee!