Sega Addons= fail.
I dont remember an addon which improved graphics and was succesful. The N64 was planned right from the start with the expansion slot for the ram.
One game utilized it and the game was expensive. Because of the 4Mb ram addon.
USB 2.0 is to low bandwith way to low. For HD gaming. Where is the point designing an addon so people can play HD games ? A DVD drive is cheap. The hardware in the wii is cheap. The new addon would need more expensive hardware and be more expensive then WII.
Wouldnt it be better to make another console and sell Wii and the new console at the same time to get control over all markets.