I've gotten USB Loader GX, Wiiflow, WiiMC, and Retroarch to load from 3TB FAT32 from the real Wii as well as the vWii. Wii games work perfectly fine.
Like I said, the only things don't load are the emulators such as FCEUGX, SNES9XGX, VBAGX, Wii64/Not64, GenplusGX, HuGo, and WiiSX from 3TB...