I'll take the gun case. Reply to this (or PM me) and I'll PM you my cell number so we can decide where to meet.

Use active braking MOSFETs. The way AB MOSFETs work is by having two separate MOSFETs setup in a half bridge configuration (you can Google this or request I add more detail). When there is no input (trigger not pulled), the motor is braking. When there is input, the motor is shooting. The brake does not "reverse the polarity" as I've seen on other forums. All it does is short the motor terminals together. When the motor is spinning and no power is supplied to it, it becomes a generator. All you're doing is dissipating this energy electrically instead of mechanical. AB has negligible effects on your motor. AB is a method used in the automotive industry for sunroof motor, window lift motors, windshield wiper motors, and more. The brake will take effect when the cutoff lever disconnects your trigger contacts and stop your motor pretty close to the end of the cycle. 

As far as pulling the trigger a little bit to get one shot, I would simply modify the trigger assembly to lower trigger distance.
EDIT:
The reason why there isn't "cycle completion" on stock guns, upgraded guns, or guns without AB MOSFETs is because of the moment of inertia of the motor armature, shaft, and gear. It actually causes overshoot, especially if you're using a low powered spring, high powered motor (neo), or high power battery (>9.6V). Undercycling does not happen because the cutoff lever is mechanically switched by the sector gear.