I do think the shoulders are hard armor, not leather same as the gaunts as you see rivets in it. And I think the idea of is the black "undersuit for arms" a separate piecedoes not really matter as long as the look remains faithful to the source image. If they're separate pieces I think it's more comfortable and manageable. I did see your comment about his armor taking the shot but as tight as the vest/armor/top is, I cannot see that hole top piece being hard armor like a TK. It's just not manageable in the real world.
And the boot front armor does need to be able to bend so I think leather is really the only option, and if you look closely at the high res image of him stepping the details are actually grooves as shown by the lighting/shadowing and not raised "ridges".
If you want to pitch in with the CRL, I'd pm ionicdesign, he's one of the LMOs and the main gatekeeper of the process.