I've been loving reading through this thread. I'm looking for an interesting 4WD buggy to replace an old Schumacher Bosscat works I sold a decade ago (it was classic even then!). This is very interesting especially now there are new re-releas RC10s out there.
Is Shapeways the only option as far as 3D print goes? We contract out a fair amount of 3D print stuff (medical mostly) and there are certainly some places better than others. I guess Shapeways provides a method to offload the ordering and manufacturing process (and generate a small income from the sales) but is it worth trying someone else like
https://www.3dhubs.com/, or
http://www.sculpteo.com/en-gb/, or
https://i.materialise.com/materials. We actually used a 3D printer in California called Forecast3D for some unusual medical grade components we needed. There were the only people in NA that could get us a fully biocompatible material.
Secondly, it doesn't cost that much to go from a 3D print, to short-run moulded parts, but you'd need the orders for conversion kits up front I suppose. That solution would give you more control over the material, and likely more robust results.