to sum it up all, the logic boards behind all the hardware you see, seems to share a similar functionality. The main problem with wii is... the code must run on the "hipervisor" cpu, or the starlet, and you gotta basically build a low level system driver (for the whole wii) when USB 2.0 is enabled(most sysbus is connected directly to starlet, correct me if i'm wrong)... or modify an existing one and inyect your own modules..
generally speaking it's a nightmare if you're testing code and the thing freezes up the entire system becase a simple bit messed it up all. So it's not that easy to figure it out