In long mode, its no different from any other design in that respect. In short, it would have about 30 degrees of rotation before the derailer would hit the dropout protruding behind the UDH, but i think that's plenty, and in many cases i think chain tension would restrict the amount of potential rotation anyway?

 Nice. Clever solutions. So the rotational stop is there for the hanger itself. Is there enough room for the derailleur mount to rotate and not hit the frame?