I thought about that, but I decided that it made more sence to use the PWR JMP to turn the computer on and off since that's what it's designed to do. Yesterday while I was testing my wiring (still build the carputer) I noticed that I had no way of turning the computer back on without turning the car off and back on. Kinda frustrating.
I am planning on adding a ACC bypass switch and probably a master kill switch. I haven't decided if I need a Reset switch yet.