Sure. Program a small arduino style board that controls a relay that's in-line with one wire on the coin door switch (so it can open that switch programmatically, but not close the circuit if the door switch is open) and also have that board connected to two volume control switches --I think you can get all of these from the coin door interconnect board on wpc and later but I need to check a schematic.

Anyway a the simplest operation is to poll the new volume buttons and when closed, briefly open the coin door switch via relay, send the volume key to the wpc coin door board, and wait until the new volume button is open before restoring the coin door circuit via the relay.

Must be more complicated than that or someone else would have built it...right?