Now I haven't whipped my DC emulation scene out in over a year, but as I recall there is no cocktail/screen flipping options in the DC mame port.
Still, it's a cool idea and most classics work pretty well in the emulation scene. The sound is off on a lot of them though, but if you are looking for a budget way to do it, I say go for it. Just make sure you leave a way to get to the DC Power, and maybe you should build the cab so the controls are on the same side for two player games. I know I've seen some like this.
Are you just going to use a VGA Monitor and speakers? Man, that sounds like a real simple build... post how it works and maybe I'll want to build one too!
Good luck,
Matt