Mewtwo had a unique moveset and it didn't stop the swing of the axe. And Mewtwo didn't come with any legal mumbo jumbo or potential negative promotion. Again, I understand why people would want him back, but his moveset can be gifted to someone else fairly easily. Advance Wars would be a great fit, I liked that idea as soon as I read it on this forum, a cut and suture all in one.
Mewtwo's moveset was modified to fit lucario. They're not identical, but I thought it was pretty obvious that he was inspired by mewtwo's moveset. If we lost any characters this time, I expect their unique gameplay will be transposed and 'evolved' on to a new character. Snake's moves being put on an advance wars character makes sense, so does Ike's moves being transposed onto Magnus from Kid Icarus uprising. Just tweak the visuals, change a move or two, etc, and you can keep that character's uniqueness while keeping them up to date. Also,I'd like to Make zelda unique, and transpose shiek's moveset onto Skyward sword Impa.