Well I guess since I have some experience with electric riggers, (all of our rigger designs have been national champions) heres my opinion.
Riggers draw a lot of power. A 20 amp speed control is probably not going to last long even on a stock ROAR 27 turn motor.
Forget the micro switch idea. Even a multi speed micro switch set up will be hard on the motor. Also a ROAR motor is not the best choice for a rigger. The timing is way to far out, and the RPM is bare minimum.
Riggers require a lot of prop RPM to get up and go.
Find yourself a good electronic speed control. The Griffin 55 is a good controller. It has BEC which eliminates more weight.
RTR a 6 cell rigger should be about 2-2.5 lbs. The extra servo, microswitch, and mount, will put you way over this weight.
Peter
www.climatemodels.com
(For the best rigger kits)