First a couple of points: Your RV is a Gulf Stream but it's on a separate manufacturer's chassis, probably Spartan or Freightliner. They add the suspension to the chassis, not GS. The dump valve function is probably tied into the leveling jack function, which is added by Gulf Stream. What you want to do isn't that hard, you need to trace the wiring from the leveling jack dump button and install a second switch to trigger the dump valves. I'd be very cautious about that switch, it should have a bright light or annoying buzzer when energized to remember not to drive off with the bags deflated. It would quickly ruin your U joints, transmission end bearing, the air bags, and possibly interfere with turning corners with the bags deflated. Energizing the dump valves from a second switch might also need diodes added to prevent energizing the leveling jack system. Not for sure about that, but I'd sure check.