You've got the thinking right. Regardless of where the piston stops...it's going to have to be pulled all the way back and let go for the next shot (so theoretically the same as any other shot).
No. That mosfet will not do what you want (complete the cycle on full auto). The only systems that do that now are either custom built "one-offs", SystemA's PTW/Revolution circuits and the very very new Airsoft Systems (AS) Smart Control Unit (SCU).
don't mix up Active Braking (AB) MOSFET units with what you want. AB will stop the system as soon as possible after the completion of a shot...but only for semi-auto, not full auto.