Just thinking out loud here so take it with as many grains of salt as you please...
IMHO, when you break down RCC to a core level it is people with a common interest sharing information for the betterment of the community as a whole. With that being said, I think it would be neat if you were allowed to use any tools you have at your disposal during these challenges. But you have to document your "process"; napkin sketches, laser scans, CAD files, CAM files, raw stock roughing, setups, fixtures and finishing... Like CHUD talked about, everyone will get to see what really goes into taking an idea and making a finished machined part. I can guarantee that someone will learn something that makes their next part easier/quicker to make. I have no formal training in machining or 3D CAD but was drawn to them both for the problem solving challenges they present.