I agree with you if i'm honest. But the biggest problem I can see is the making of the hubs. I don't have much in the way of machinery/tools, so I'm pretty limited to 2D laser/watercut parts or 3D printed nylon parts, or whatever I can cobble together from bits and bobs. Unless I can think of an easy way to make/find a hub with a keyway and grub screw that fits the saturn drives, its easier for me to do a belt drive. For the belt drive I can order a timing pulley from belting online, have them bore it out to size and add a keyway and then make a nylon/alu hub for the castor wheels myself.

Extremely open to suggestions on alternatives btw, I'm just trying to be resourceful with what I have access to!