Did this on location once, day for night where the windows would be in frame. Thick ND on the windows, I think at least three layers of .9. Then a 6K PAR for the lighthouse sweep. We started with a spot lens but it wasn't quite enough punch through all that ND so we ended up going sans lens. Unfortunately I can't find the footage online, but I recalled it looked pretty good. There was probably a better light for the job but it was part of a feature and the 6K was in our standard package and they wanted to avoid day-playing additional gear. In any case, we just panned across, then tilted down and panned back below the window to the starting point and panned across again, no spinning reflectors or anything.
Since you have the luxury of being on a stage, maybe a 5K or 10K Molebeam projector, depending on what interior levels you are balancing to?
I guess it will also depend on what you are seeing. Do you just see the beam swipe through, perhaps edging a subject; or do you actually see the wall where the beam hits and watch the spot swipe through, maybe even front-lighting a subject as it crosses? And how tight or wide are the shots?
For the aforementioned feature, we did shoot in and around the actual lighthouse. I was surprised to learn that the actual fixture in the lighthouse was just a 150w (if I recall correctly, though it was definitely something low like that) incandescent bulb with a couple plastic fresnels spinning around it. Lighthouses are meant to be seen, not to actually illuminate anything around them, but alas audiences are still looking for that gag. The good thing is that you have some artistic license as to how you want your beam to look.
Edited by Toby Orzano, 05 March 2014 - 01:46 PM.