(...) Would a servo or gear motor with encoder work in place of the stepper?
Motor torque is proportional to current, so you need a certain amount of current to generate the required torque.In any case, steppers are usually the last choice, when battery life is important.
I assume that it's not regardless of size?
I have to admit that I have no experience in geared motors or servos at all.
Say, two different stepper motors has moving and holding torque that exactly suits my needs. The difference between them (despite sizes) are Amps / resistance per winding and operating voltage. I need 3 of those motors and I'll power them from a 4S battery pack (4x18650, 16.8-11.2V, 3Ah each).I'll drive them with Pololu DVR8825's, set to 1/8 microstepping. Holding/move ratio will be about 80/20%.Should I choose motors with lower resistance or amperage per winding, to keep my batteries run longer?
While stepper motor will easily handle any spikes of torque, the DC motor will not
If you can carry the 3h battery pack and 3h is enough time for you then there is no problem.Any gearbox using a worm gear is considered "irreversible" meaning that the output cannot be moved unless the motor is powered. If the steppers don't work out, look for gearboxes with worm gears.
I'd really love to know weather I could DIY something that could provide me fully freezed "stop" position, and fully repeatable movement, while using less power than just a simple stepper motor.
A servomotor is what you are looking for. Only uses the power needed at any point in time.
(...)Any gearbox using a worm gear is considered "irreversible" meaning that the output cannot be moved unless the motor is powered. If the steppers don't work out, look for gearboxes with worm gears.