Interesting idea, but Drake brings up a good point. How do you plan to handle extra credits/continues? Unless the firmware arcade cabinets use has some reaaalllllly special trickery to do this, I can't really see any way short of assembly hacks that modify the continue screens of each individual game. Not to mention continuing sometimes plays a special role in a game (ex, IN). So, why even have "credits" to begin with? It doesn't seem to me like it serve a purpose (unless you have commercial applications in mind for this - for personal use, you could just put/take money in/out at your whim and have infinite credits so...), and would probably bring about a lot of technical problems. You could easily write yourself a small game selection/launcher program and letting the selected game take over "as-is" (ie, with whatever continue system it has) until the player quits it, I'd say...
Do you have plans for this other than personal use? I'm wondering what the scope is here - sounds like it'd be pretty expensive and time-consuming for just the occasional personal use if you already have a PC that can play all these games just fine.
Lookin' forward to screenshots once you'll have started building the cabinet.
