Hmm. Tough problem. What about a couple of "tables" which vibrate back and forth at a really shallow angle, just enough to move pieces in one direction? I have gravel sorting tables with screens in mind, but the same principle with a solid table to just break down a heap into a flat layer may just work.

I think that a couple of tables, cones, and dividers (to create lanes of pieces) could do a reasonable job of turning a heap of pieces into a steady stream of individual pieces.