It should be possible to start with a spandex body suit, or something similar.
Using the multilayered approach should work really well for a few reasons.
1) Saves you the trouble of coming up with a symmetrical base suit
2) Provides the ability to add further depth to the suit
3) Add durability to the suit
4) Provide a framework to attach armor pieces and run electronics
By putting the bodysuit on either a mannequin (which many of us don't have) or just wearing it and having a buddy help, you can lay out template pattern on the body suit in the proper shape. Then create the actual pieces out of whatever materials. Then while wearing the body suit, adhere the pieces on to the suit itself with enough adhesive to not ruin the undersuit but still be able to take it off without the pieces falling off. An alternative would be to mark suit and then place pieces once the suit has been taken off. Sew on the pieces to the undersuit. You then run the harness of straps underneath your added pieces, in essence sewing them between your spandex suit and the added on pieces allowing you to attach the armor pieces to the suit.
I've only recently started building my undersuit, and it isnt very far yet. I am so far planning on integrating the following:
1) Camelbak -- should be useful for if you plan on wearing the suit for a while...won't need to keep taking off the helmet to get a drink
2) Strapping harness -- Primarily for the chest and back pieces, still figuring out a way to handle fitting the leg and arm pieces
3) Electronics Harness -- Wire jacks into the helmet and left forearm (or chest) with switches for helmet LED's and fans (if I have motivation and funding, maybe have fans run on temp circuit)
, I will be sculpting a bodysuit and casting certain secions in black latex or silicone. These detail panels will be sewn into a custom made spandex bodysuit.
