The control panel can be fabricated if needed, so I wouldn't consider that to be a huge obstacle. However, according to KLOV:
A Nintendo Punch-Out!! cabinet can be converted to a PlayChoice 10 (dual monitor version) but a two-player wiring harness must be acquired.
That sounds like something that might be tricky to scrounge up. In any case, good luck with the project, I'd love to have a Playchoice 10 myself.
-S