@edmaul69 I appreciate the clarification. Not finding any information on the subject was annoying, so being told it was impossible without any explanation as to if it is actually impossible or just unlikely was rather insulting. I admit I currently have very little familiarity with I2C and haven't done much Linux wizardly in a while, but it seems i just have to wire everything to the correct pin, figure out what each button press does and map that to a controller function. Not impossible.
I should note that this is actually a fake console - though everything except the motherboard is identical. The controller doesn't work on a Wii, but the second controller I bought does, and both controllers plus a Classic Controller pro all work with the NES Crassic. I don't expect this to make it any more difficult then if I had genuine controllers, but it may mean my driver may not handle all the extra checks a genuine controller wants.
Currently I'm waiting on a soldering gun and some female pin connectors to come in the mail before i start.