How do the individual segments "combine"? Are they individual robots? If so, you may have to sacrifice the quality of the individual sections to create a greater giant mech. One thing you could attempt is having the limbs fold into the the body of the individual robots, hence making it look more armoured. Or, a custom-made body which could fold open, being one of the giant mech's limbs, with the folding feature acting as the knee/elbow.
In all honesty, I don't think I can recommend anything without pictures. Good luck with the project, I'd love to see it when you're done :)