hey ozmodchps, i don't know if you have tried it already but apparently someone has managed to get the retail SSBB working on a WiiKey modded Wii by doing the following:
1) Enter the Disc channel from the main menu
2) Insert SSBB disc
3) Wait for the disc to be detected
4) Press the power button on the remote to put the Wii on standby mode
5) Turn the Wii back on
6) When the main menu appears, the disc channel should already display SSBB. You can then start the game. THIS IS UNCONFIRMED, though.
However, now that a new Wiikey firmware is imminent, it doesn't matter.
26/03/2008
Okami
I don't want to wait in vain for your love...