yeah, the older games are quite small, i forget the exact sizes but roms for nes were <1mb and snes prolly no more than 6mb (the newer gba games go up to 11mb but they are a bit more advanced than the snes was), the n64 games are where we'll run into space issues prolly
The Virtual Console has me intrigued. I wonder if maybe considering that the wii is Wi-Fi and the fact that most likely its going to be networked with a computer if you can store these files on your PC. Maybe you could even purchase and download them via PC and move them to your Wii.
Yea the best idea is that where you go to your local gamestop or ebgames and buy a card that has credits on it for the Wii online for you to purchase games and stuff. Hopefully thats what Nintendo does.