Hi I checked the ultimarc site and it does state there is an optional 4 wire harness that can go to a ipac keywiz etc. and act like it is a 4-way joystick.
if that is the case you would hook the 4 wires from each joystick to the center row of termnal/poles on each of the 4PDT switch and on each end of the 4PDT switch goes your analog and digital signals that would run to the dc gamepad pcb's.
as seen in my pics I make everything on DB-25 including the actual arcade controls and they connect to DB-25 switch box's so arcade,pc,dc are all on a switchbox's for the controls and video for each system set running.