Very nice job! I'm planning on doing something like this too (almost did it for the mod challenge but ran out of time).
How does it handle start up? Does it go right into the mame app? What about switching games and such?
Rewired original switch to a back lit arcade switch - starts up fine.
Loads up, then straight into MacMame (the menu bar is also hidden - a bit neater)
Switching games is all done through joystick and buttons presses using quickkeys and stock Mame controls.
I'll be adding a write-up here soon - dismantled it last weekend to do final tidy up so hopefully will make good progress this weekend...