On a Plasma unit that has a CNC option, it is started by a contact closure at some point, so you should be able to do the same thing with simulating the torch switch.
You can get away without water cooling as long as the duty cycle is not high i.e. your off time is longer than the on time.
Usually the sequence on a CNC unit is the pilot arc is initialized and once transfer is made to main arc, motion commences. Also automatic height control usually comes in once the travel has started to avoid the torch diving through the initial pierce. Your travel feedrate depends on your available current and material gauge. You should get an idea what your torch will do when you cut by hand. e.g. I believe 200 amp comercial units run at around 100"/min for 1/4" ~ 3/8" plate.
Al
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.