Bunch of info after I did some digging:
- It should be easy to get e9x m3 paddles to work. Physically they will mount correctly because the wheel did not change between N554 and N55 e82 cars. It might require some minor electronic work like changing resistors as noted, but that should be easy to figure out. I suspect it's a completely passive circuit in there.
- Finally figured out the mystery that the OP asked. I was very curious why the F3x paddle looked everywhere so similar to the e82 paddle that was posted however the mounting surface was clearly different. Well the answer is actually very simple. BMW must have been in the process of changing suppliers of the paddles or simply generations of the paddles when it chose the N55 DCT paddle for the e8x. Essentially they used the new paddle and but needed a mechanical adapter to mount it to the "older" style steering wheel that the e8x was using versus the f series. This is possible because the new paddles are notably thinner that the old paddles allowing for a plastic adapter to be used without adding too much bulk.
Sometimes a picture is worth a thousand words:
So TL;DR just as the OP suspected you can most certainly use the F8x paddles on a DCT e8x car. It will require that you remove the paddle from the vehicle. Remove the plastic mounting adapter and then separate the electronic portion from the physical paddle. Also separate the F8x paddle from its electronics. Put everything back together with the F8x physical paddle, stock electronics , stock mounting adapter. Bolt it back on the steering wheel and go about your business as usual. Very straight forward process, with the paddles on a bench it would take less than 5 minutes to move all the parts around.
I am considering picking up a set of F8x paddles myself but honestly I don't really like them look that much of the stock f8x paddle. I feel like immediately I would have to swap to an aftermarket extended paddle, which means I am paying hundreds of dollars just for a little plastic mounting surface to bolt e8x electronics to an aftermarket F8x paddle. If I do buy the F8x paddle I will probably try to put something together in CAD so I can just print out the plastic bottom mounting surface so no one would need to spend hundreds just to get it. I guess in theory I could just measure what I have now, order an aftermarket F8x paddle and then modify the mount in CAD once I have the dimensions of the paddles. Hmmm... Decisions decisions, too bad aftermarket F8x paddles are like $230 minimum. They are under $100 for the e9x
