Looks awesome. I'm working on the radial hexapod body from lynxmotion.
I've been reading alot on the internet (probably too much for my own good because I have too many ideas floating around in my head), but I digress.
The Mega looks like the best solution for the robot for starters at least. How did you modify it to control the extra servos? I can't find any details on that aspect of using the Mega to control 18 servos.