Naomi Crazy Taxi Outboard Control Panel?

[MasterOfNone]

I've been stockpiling parts and hope to live long enough to get around to this project..., a pretty crude and limited Naomi multi-game. I just want to build a box around an old Naomi Universal cab 2-player control panel (couple of joysticks each with three buttons, plus 2 game-start buttons that could be left unused or repurposed) and tether this box to a Crazy Taxi I/O board without disturbing the original dedicated Crazy Taxi controls, and then be able to play a few other Naomi cartridges I have that already run fine, but just need the right controls hooked-up to the right pins.

If I can find the pin assignments for the cartridges I have, seems I'll eventually get something working, but posting here just to see if anyone's already done it or has any tips.  If I was super-lucky, someone out there would be selling a ready-made Naomi splitter Y adapter harness of sorts that allows two different original Naomi control panels to be simultaneously plugged into the same I/O board..., not for use simultaneously though.  If the Crazy Taxi cartridge is in, the tethered outboard control box would be tucked away unused, and if a joystick game was plugged-in, the Crazy Taxi controls wouldn't get touched.  I'd just be sitting in the Crazy Taxi seat with the outboard control box on my lap. 

I wouldn't be swapping out game cartridges too often. I'd leave the same game in for months at a time.  I've already done the Jambo Safari thing, with appropriate jumpers on the I/O. Waverunner already works okay without any modifications at all (except the accelerator pedal is full-throttle when untouched and off when floored, which ain't so bad to play with.) But, need to add joystick/buttons for Tetris, Tennis, and maybe other cartridges I eventually pick-up... Yeah, I'm sure there are easier and better ways to play these games.  Just a whim to do it this way. I might be talked out of it if you try.   Thanks!