Alright, can I say that I'm in love with theater troupes and how amusing they can be, especially one that's basically starting up with it's first "major" production (if I've got Mnemo's premise right).
As it is for me right now, I'm taking an extended break from WW, because I can't do any sort of commitment on the weekends. However, Mondays-Fridays, I'm anyone's who wants me. If someone will be able to pick up my character on Saturdays and Sundays, I can be a regular player. If not, then I'll begin thinking of some minor roles.
My thought for a regular character, would be the loud, arrogant member of the troupe, who thinks he's the biggest star of the show, and tries to hog the spot-light. I can imagine a character, who has as much humility as Denethor, playing Sam or Gandalf. That would go over well, in front of the King.
And if I feel because of my inability to commit any writing saturday-sunday, for minor roles, I was originally thinking a theater critic from Minas Anor. However, since we're leaning towards the Renaissance model, I think it'd be too early to have any psuedo-professional theater critic.
Instead if you're looking for cameos to focus on the historical accuracy of the performance. I've had an image of Imrahil, in the "changing" Gondor would be fond of the arts. So, I'm thinking a Swan-knight of Dol Amroth, who went with Imrahil to Minas Tirith, would likely be interested in attending the big show?