Personally, I used a telephone jack (4 pins) and wired 2 of them to the ext. LED (power LED) pins on the M2-ATX, and then wired the other 2 pins directly to the power switch header on my motherboard. Using a 4-wire (2-line) telephone wire I ran to the front of the car I created a box with another phone jack (I modified a standard surface mount box) with a switch and LED. This way I can see the LED to tell me if the system is on/off/suspended, and use the switch for on/off/hard-off/suspend.
I can kinda visualize what you're talking about now. I had to go get a phone wire, and it all made sense, although I am still wondering how to bypass the shorting of the m2-atx.
It was a good idea to use a phone wire to mount a switch and power LED. Thanks for the idea.