ORIGINAL: dirtybird
A motor with a jackscrew is an open loop servo. If you were to use it in an aircraft you would quickly decide it is unsatisfactory, just as the modeling community did. Our early reed system used open loop servos for elevator trim. They proved hard to use, A closed loop servo is much easier to use.
If you are afraid of the reliability of model servos, get one designed for UAV's. It will cost you a bit more though.
Exactly what you want for this, open loop. You are the feedback loop in such device, you stop the input when the trim is where you want it. The KISS principle.