weirdami, Actually, resin would prob. be too brittle for it. (Unless there is a special type of resin that is semi-flexible, I know the polyurethane resins that I have used aren't.) Trapdoor covers have to flex a little, at very least at the catch. Now if someone had a few grand* to get some made in injection-molded plastic, and make some A4KT drive bay covers while they're at it :-D
*I believe companies that do this require 1,000 units minimum.