I would recommend:
1) Move the spinner to the left of the trackball. It is surely going to get in the way if people are playing "Golden Tee" and other trackball games. I would think it would hit the forearm of the person spinning the trackball.
2) Put left/right flipper buttons on the side of the control panel so you can play some Visual Pinball and Future Pinball tables.
3) You did not mention what buttons 24,25,26,27 do. I am assuming they are player1 coin/start and player2 coin/start buttons. If this is the case, you might want to consider putting left/right click buttons so you can use your trackball as a mouse. Some people may say to simply have a pullout drawer in your control panel which has a mouse in it, but I find having mouse left/right buttons on the control panel itself a necessity when playing some PC games on the cabinet (ex: Feeding Frenzy). Also, the buttons are just useful when you are configuring stuff.
4) Make sure you have a PAUSE button on there so people can go refill their beer or get rid of the beer they already consumed

5) Some admin buttons like Quit and Reset would be nice as well .....
Oh yeah .... welcome to BYOAC !