There is an adapter that may solve this problem, with it you can use ps2 control connected to a gamecube output, now it remains to be seen if there will be no interference
Look at this link...
I managed to get back through the priloader, I don't know much about Wii, my screen was just like the picture, a doubt, in case the menu navigation is done by the gamecube control? If so, is it possible to use USB control or not?