Add an assembly that allows exchange of the dpad and controlstick's position. I've used an N64 controller only once, but the middle grip was pretty badly placed and this solution should never again be used. Do not make the dpad the default control like the PS has, that is just idiotic in the age of 3d. Sure, it's good for fighting games, but what about the rest? Analog controls are a lot better for most games (hell, even some GBA games could have used it!)
[OT]IMO the current concept of fight controls is obsolete anyway. In SSBM you could just control by "intention" (i.e. upward attack = up+attack, forward attack = forward+attack), while in other games you have to use 10+ button sequences to do certain manoeuvres. I prefer the philosophy that a special isn't a super powerful move, but a move with a special purpose (e.g. attacking a large area below you).[/OT]