Make sure to check and see if the spinner gets in the way of player 2's joystick arm. Can't tell without the drawing at full scale, plus it could vary depending on how the user holds the joystick.
Also, a single exit button might make it too easy to accidently exit a game. How about map it so you need to press the pause & the exit button at the same time (at least in mame), or use an encoder with a shift/shazaam button (and pause be the shift button)?
I like the administration buttons on your CP. IMO, I think it's a Bad Idea to have any of the action keys double as administration keys, but I know others disagree with my veiw. I just hate having any chance of being in the middle of a game and someone (me or someone else) press a key that will make an action button that's being used in the game: exit, bring up the mame UI, reset, goto the test screens, or otherwise mess up the game (but pausing is okay). Killing a game accidently once a year is far too often for me.