I can appreciate his dedication as a fan in wanting to see the set and be envious that he got to and I did not. However, I will be very disappointed if I have to see his mug on screen at any point, even for a second.
Maybe they stuck him in a spoof easter egg akin to the MTV's Council of Elrond with Jack Black?
I would not be surprised if he was under heavy prosthetics (assuming he's in the movie at all), maybe some background dwarf with a throwaway line. They're too smart to not get that he's far too recognizable of a face to just shove in there, it would completely take everyone out of the film.