If it's a generic (Hooray for Dynamo!), anything is fair game. Put a fishtank in if you want, it's just a wooden box.
If it's a dedicated cab, and it's still reasonably intact, then a full resto or cosmetic resto (PC inside, resto outside) is the way to go.
If it's already been converted to the point that the only thing that remains of the original is the shape of the wood, then the heck with it, unless it's a truly rare cab. I mean, there are a million Pac cabs out there that have been sanded down, painted black, and had the control panel drilled in 20 places, and the wiring and PS converted to JAMMA and a switcher. No reason to try and re-build the Pac Man from that POS, MAME it if you want, 'coz it's already been maimed. It's not as if you're damaging it any more by putting on blue t-molding and a trackball.
But if it's rare, then you oughtta try to bring it back, or trade/sell it to somebody who will. There's so many generics and bad conversions out there that there's just no reason to go MAMEing an I, Robot or a Joust coctail.
And if it's water damaged, scrap the dang thing- somebody needs the parts for their resto, anyway.