If I understand you correctly, you have some sort on safety intelock on your spindle controller.
My X2 had something similar. You had to turn the speed dial (rheostat with integral switch) all the way past zero to reset the controller befor it woudl start again, making it basically incompatible with Mach.
Your switch is separate, but the function seems similar.
On the X2, the switch energized a relay on the controller board that activated the controller. Once energized, the relay stayed latched unless a fault kiled the power holding it closed. Then it would stay open until energized again by the switch. Hope that made sense.
What I did was follow the wires from the speed dial and then the traces on the contoller board to find the relay and I simply figured out which pins energized the coil and put a jumper across the pins so that is was always on.
I don't use that controller any more so I can't give you specifics, fried it . . . twice . . . long story . . . but not related to the above mentioned modification, which solved the reset issue.