I would love that!
Though flying types and fully aquatic pokemon would be hard to incorporate into super smash bros. Either pidgeot loses his beloved flight skill for a simple fluttering (the closest they could get to flight is kirby's flight, and that would be kind of demeaning for a majestic pidgeot) or it can't be used at all. I guess they could be enemies, but I bet people will lament the loss of their beloved pidgeot/swellow/staraptor and instead having to knock it out of the way every time. And would the fearsome gyarados have to crawl around the stage like an inchworm? Stages like the Great Bay would be illogical. Goldeen has to awkwardly flop on land, then it drops in the water and dies? Aquatic pokemon couldn't even be enemies. Unless they mimic the pihranas from Rayman. And what would the items be? Maxim tomato becomes super potion? Bunny hood becomes quick claw? And think how awkward it would be for big ol' regirock to be trying to move on a small stage. Or what happens when diglett is star KOed? Would caterpie's third and fourth specials be nothing? Everyone would need sky uppercut as a third jump in case they fall (though I guess they could simply make any third move into a third jump if nessecary). Gastly would be useless, just floating around, everything just going through it. Also, all the pokemon would be near the same size. Look at 8 inch kirby compared to 1 foot 4 inch pikachu.
I also get the idea that some moves wouldn't work out well in super smash bros style. Imagine: Kricketune uses bide. With kricketune immobilized, the enemy could easily get a couple free hits, and then a hop skip and a jump and they're on higher ground, avoiding the retaliation completely, leaving kricketune damaged for nothing. I guess it could work like Game & Watch's bucket, but a pokemon attacking after using bide?
Of course, a big problem would be in the fear to change from the original battle idea. I once had an idea for a similar game (where the player could be the pokemon and could move it around) and I suggested that how speed works would be that once a pokemon's speed is sufficiently lowered by an attack, the pokemon be not allowed to use attacks until the now faster opponent has launched an attack. I regarded that as stupid for the obvious reasons.
Speaking of speed, I've come up with another problem. Look at SSBM's battle style. Big, tough, heavy hitting bowser is slow as a turtle. Shiek has no powerful attacks to speak of, but she is one of the quickest characters around. Now look at pokemon's. Evolution gives a pokemon higher attack, higher defense and higher speed. See my problem. The weaker pokemon would *usually* be slower than the strong ones, leaving things really tough for them in battle. Though I guess Speed could just not be translated from the games, as it was for SSBM (pichu's quick as anything in it despite his Speed stat)
Many technical problems, but if someone managed to get around that, I would love that. I would like a game where you could upload pokemon from your game to the super smash game. I'd love it!