GX is one of my favourite games, but I agree the attack option didn't really work- I think its because the analogue shoulder buttons couldn't be tapped twice in the same way as the N64 ones, so they had to map it to the X button
The wii version should be controlled with just the remote, I think they should be able to make it work well, after all the remote is very sensitive. The attacks could be done with a quick flick in the direction of your opponent. Using the nunchuck adds unnecessary complexity, and I think the classic controller is a non-starter, I don't think they'll use it for any games, even smash bros, as it adds to consumer confusion...