Ah, nice! I wouldn't've thought of putting Pichu under Pokemon Trainer... Actually makes quite a bit of sense. That would be a pretty neat way of sneaking Pichu back in.
For Mewtwo dying, I really don't know... I could certainly see the likes of the "darker" characters being killed off (Ganny being one, as he's already died a number of times in the Zelda games), but Mewtwo... Sure, he came close to "death" in his anime special, but it just doesn't seem to really match him. It's almost like trying to kill off Bowser, King Dedede, or Wario, even. Just doesn't really sit right. The close to "death" I COULD see him reach is being turned back into a trophy temporarily, but that's about it (given trophification is like death in the Smash World).
Ah. If only Smash could be that dark. I highly doubt Sakurai would ever dig himself into a hole that deep, though.
Regardless, Mewtwo and Cut Companions for Smash Bros. 4.
And an Adventure Mode that doesn't take away from the roster this time. You'd think they would've made Primid playable for all the effort Sakurai and co. put into making them... (Like how Auroros were supposed to be Assist Trophies.)