To solve the major problem of replacing the belt, a spare belt will be secured around the axleshaft, ensuring that no pulleys or collars rub against it. If/when the main belt breaks, the spare is easily dropped into place and adjusted for tension.
I inquired with an online company who can fabricate custom pulleys. I might order a twin pulley which is siamesed together, using a 14-tooth and 15-tooth. To change pulley size, simply loosen the drive pulley, align the new pulley size to the belt and tighten everything up.
Voila! New gearing ratio in minutes!