I honestly think mewtwo is viable the way he already is, but you have to be careful. You have to base his neutral off of D-tilt, nair and ledge cancels. Hard to learn, but VERY fun one you get the hang of it. I'm saying thins out of personal expirience, but if we had sombody like AmsA in smash 4 (yes I know he plays Greninja) but mastered Mewtwo, everything about all charcters will be reconsidered