Luxology's Modo 401 is the 3D package. And I just used its default renderer. I rendered it out at 3500 x 4529 at 300dpi and it took hmm I would guess about an hour. I ad an issue at the time where the processing was fine but I would run out of memory (only 4GB ram back then) So I think when I found the middle ground of quality vs not running out of memory, the renders were taking about an hour I think. This was rendered this time last year. Just finally getting round to posting it about the place. Modo is now at 501 and twice as fast rendering and now 64 bit. So would probably render this in like 30 mins I guess.
The heel and foot as seperate parts attached at the ankle joint, it's very clever, and works great. A robot wouldn't wear shoes, and normal anatomy doesn't lend itself to high-heels. Also having a high-heel "foot" would look quite odd on a robot. Your simple(and well executed) solution is perfect, I can't think of another way to pull it off.