Timing belt.. toothed gears & belts... are a simple way to change ratios and do a positive drive setup.

I have some fist sized, Pittman #14204C637 servo motors, 12 volt DC. They are very high torque, low speed motors. Go with a MIXER radio setup somehow. It will solve the most problems in 1 shot. Use 1 joy stick that has 2 channels spring retuns.