Hi Ed
I kind of agree, my thoughts on a gas powered pre-rotor (down on the mast so as not to change the balance of the head) is that it would add the feature of learning how to use a pre-rotor to the training , start out with hand start and work up the rpm to above flap speed and once you have this mastered then start using the pre-rotor to get that experience, and probably double the flight time with quicker take off's. Valuable training at a lower costs, especially if you have good experienced drivers on the tow vehicle
Tony