google "thirding" term. If you are brave one you can look directly to polycount wiki cause it is covered there as well. You know polycount have wiki as well right? EDIT: does not matter what engine are you using... It is general technique.
I was thinking of doing the folding geometry, but I have too keep my polycount down. I wonder if texturing each modular piece separate would be even better than an extended texture? If you figure, with occlusion culling, the modular pieces that are seen at once, may not always be all parts, so only rendering the modular…