i dont know much of anything mind you...
But thinking about your limitations, I first think of vinyls type of material...
So if a vinyl type material was going to be used you could not cut or necesarily mould,
so that leaves heat, hot stamping as the way to impress a design into something like that...?
Then theres rubber, you could make in leather and then try and cast the originaldesign (ex; rubber spiked brclts) ...
Good luck, sounds like a great challenging project, love to see what you come up with
eta, i think silicone was what i was thinking....make a mold out of a TAP resin product and cast in silicone (rubber), something blah blah like that...