All the issue mhkohne mentioned can be avoided by going with a strictly mechanical switch.
But as noted no such beast exists, so you'd have to make your own.
I actually looked into this years ago and designed one that I have yet to get back to building, thanks to some personal issues.
It'll be a twelve game switcher. Power would be cut when the knob is pushed in, which you'll have to do before you can turn the knob to one of twelve positions where you release it, allowing it to spring back out restoring power. It'll be done this way so that the breaking and making of all connections will occur when there is no power applied. (So there is no arcing or scoring of the phosphor-Bronze connections to worry about).
And turning the knob to switch between games has a dual purposes in that wiping occurs of the contacts between the twelve positions.
Twelve small extension harnesses would be needed. I just have to decide between "store-bought" JAMMA finger boards or finger boards I'll have to make myself, since they will be a permanent part of the switcher.
I know that the fingerboards Bob Roberts sells don't have a high cycle life because they weren't made for a lot of connecting and disconnecting, so friction would too easily damage the traces over time. However I do have some fingerboards that I picked up via eBay years ago that are more durable.
The plans for this switcher are all but done.
(I guess that an easier, but dirtier way to switch between games would be to use multiples of those rotary switches referred to above, while making sure there is no power applied when changing between positions).
Darren Harris
Staten Island, New York.