Well, I can tell you that as a martial artist I have never seen pauldrons or shoulder pads if you prefer. Plus since you don't need them for actual protection you could just free hand them out of several layers of foam then treat them with plasti-dip or something. I haven't done much with foam...
If I were you I'd see if I could contact killbucket himself and ask to buy the plans. He used to sell them on his old site. If that doesn't work I'd look into airsoft dedicated forums. They would be able to help you fine tune the internals etc.
On the airsoft side of things I can tell you that it is impossible to build a minigun that fires properly. The light bbs are fired at too low a speed to exit the proper barrel without going wildly off course. The way around that is to fire the bbs out of the center of the gun while the dummy...
not to derail the thread, but in a similar vein are there any resources on the Russian GShG-7.62 machine gun? It's essentially the Russian version of the m134.