I dont think they need to make a remote for turning it on and off, but standard wireless controllers would be nice. I would also like to see the controllers be able to use the GBA-SP screen. Instead of having to use the GBA-SP as a controller, it could slide into the back of the regular controller, and the screen could stick out on top see you could see more info.
I think that it either has to have 1) a hard drive for saving games, 2) 4 ports on the GC2 for memory cards, or 3) memory card expansion slot in the controller. This way if you are playing a four player game each player can have their own settings, custome characters etc.
Mini disks are fine, so long as they can hold the games. I dont want to have to swap disks to play a game just 'cause the disks are small. If I dont have to swap disks then they could use square disks for all a would care.
Backwards compatability with all GCN games and accessories is a must.
Something else that would be nice is to have dual audio/video output. That way you could play multiplayer games on multiple tvs instead of using a split screen.
At launch the GC2 needs to have several first party titles (Mario, Zelda, Pokemon, Metroid) to name a few.
Another thing I would like, Nintendo could start doing this now to really make me happy, is to release demo disks each month. Release them with Nintendo Power, or some other magazine. Put one playable demo, one or two movies, some commercials etc on each disk.
The most important thing is that they must release before or very close to when Microsoft and Sony release. They cant wait a year or longer to try to catch up.