Interesting. I came up with a similar type project myself BITD... When I was in my late teens in the 90's after I bought a Turbo Duo with an Avenue 6-button pad, I had an extra Duo pad left-over as a result and I came up with the idea of taking the PCB out and putting it in my old
NES advantage joystick to see if I could make it all work, turn it into the "NEC Advantage" joystick, that way, I wouldn't have to ever buy an actual NEC Turbo stick, etc. =) Well, it worked, although the tricky thing was the atypical wiring for the Duo cable, copper strands with string in the middle; it was hard to safely strip it and twist it with regular copper wire of normal cables and have a reliable connection/joint. Anyway, I've been thinking I might raffle it off some time here since I never really used it (thought I would). I recently went back a couple of months ago and soldered the joints in the wiring properly after making the cable 12 ft. long; I learned how to better strip that Duo wire so I got it working perfectly with no faulty/flaky connections. Funny enough, it all works, analog potentiometers for the turbo effect, the slow-mo button, etc. I was surprised that I succeeded when I first did it.