In stages such as Halberd where the background is of the moving ship what would the Pokemon Trainer (Red) do, and in Rumble Falls would he fly up or something or would he magically swing from vines? In the bridge stage where it crumbles what does he do if he's standing on the part that crumbles?
from what I've seen so far, red seems to stand directly behind his pokemon, implying that he moves along with them. I suppose he would jump along with his pokemon, and if they fall down, he falls down and gets regenerated with them. or perhaps he doesn't, and during moving stages, he just jumps around a lot. or, he could just suffer of "tails" syndrome, and dies on a regular basis, but is regenerated behind his pokemon a second later.
When you loose a stock with a pokemon does he start to flash too?
red is simply in the background, so when his pokemon lose a stock, he'll probably just look down for a second, until his pokemon is regenerated.
During the victory poses does he do something or is it all the pokemon?
since red himself is the character, I guess most of his poses will involve only himself, but I'm sure at least one of the poses will involve his pokemon.
Does he have a taunt too?
of course he should.
he should, but I dont know they will pull it off. it would take a bit too long to say "squirtle, use waterfall!" or heck, just plain "waterfall!" and have squirtle do it directly after. he will most likely say a couple of grunts, motivational phrases, and victory speeches though. it would be pretty cool if he said different switching-out phrases depending on his condition (ex. "your foe's weak, get 'em charizard!" for when opponent is at a high percentage.),
If your in a four player match and you loose first does he walk out or does he stay behind to observe the fight?
he'll probably just look down, stomp the ground, or some other angry/emo thing and disappear ala nana.
In Smashville would he interact with the villagers or ignore them?
y'know, that would actually be pretty cool if he did. I could see some easter eggs involving smashville and the trainer, such as the villagers comforting him if he loses a 3-4 player match early, or him occasionally buying items from crazy redd/tom nook.