I wired my I-pac so that the PAUSE key is also the SHIFT key.
If you press the button, and HOLD it, you get shifted functions on everything.
If you press the button, and RELEASE it, it pauses.
Using that method, you only need to have ONE admin button.
All the other admin functions can be performed using the other buttons on the CP.
I would probably throw in coin buttons, rather than using shifted player starts for the coinup because you really don't want people to be using the shift function during gameplay.
That means you will need:
(2) coinups
(2) player starts
(1) pause/shift button
in addition to however many sticks/buttons you want for the actual games.