Thanks a lot.
Good to here that #1 should be doable. I could picture my gf messing with the 4-way during rounds of marvel vs capcom just to mess me up, if given the chance 8^]
As for #2, I plan to place the shift key at the very top-left corner of the panel, so it should be out of the way. The issue people seem concerned with is insisting there is no way mame can be operated without dedicated admin buttons (coin, pause, esc, etc), but i seem to be doing fine with my "p1 start=start, p1 coin=start + select, esc=select + left, etc" setup. I was just wondering if there was a situation I wasn't anticipating.
And for #3, I do need to unplug the usb cables as I will be using both a pc and at times a ps3 in the cab and will simply swap cables to switch platforms. So far it seems to work so long as i plug the same cord in first, so I'll likely just label them 1&2 and hope it never gets screwed up.