This is something I was also wondering. If I hook up a particular button to the shift input AND a second input on the IPAC, will it work as the shift enabled function? I'd use the shift button normally but I want the cabinet to be as user friendly as possible.
You need to build a delay circuit for the second button.
Tiger-Heli had the schematic for it in his encoder review, IIRC.
As far as user-friendly goes, I don't want anyone doing anything beyond pausing on mine.
I am probably going to change shift and ESC to P1 ans P2 coin to keep them out of the way though.
Same problem, different keys.
Both players will coin up simultaneously alot, causing the game to exit while they are doing that.
I highly recommend putting ESC on one of player 1's buttons.
Most people will coin up, and start with their button hand, which makes it unlikely that they will hit shift and ESC at the same time while doing it.