I know this isn't really going to be constructive, but I would just hang tough and get the original cabinet - - you'll eventually be able to find one. even in an arcade, i'm sure they'd be almost happy to give it to you. a 6p xmen doesn't pull quarters today, and cannot be converted into anything else.
But, if that doesn't pan out, or if space is an issue, i would go completely off the beaten path: make a showcase cabinet that is just a pedestal with 6 sets of controls on top of it and a projector at the base firing up into an adjustable mirror directly underneath the control panel. pull it 7 feet away from the wall and VOILA - - best 6p Xmen experience ever, and on your wall, no less. old projectors don't cost much these days, and it can be easily converted into something else if you get bored with it.