That's a pretty slick idea. I have seen the foot releases that the EDF guys use with their bungie launchers. This is pretty similar. Someone could simplify your design and use a foot pedal to release the pin if they wanted to.

I have a Q40 plane and just put the tail between my feet. When I'm ready to launch I move one of my feet out of the way. I think Ed Smith posted this method a while back. It works pretty well and I haven't had any trouble. Matter of fact, I've had less trouble self launching than getting "help" from others.