Rich, thanks for the link. An interesting but, for now, too expensive option. (I'm keeping it bookmarked)
Jon, these won't be national acts and I am not sure how much you mean to cover with the term 'regional acts.' For the latter it is a case by case basis, and after getting a scowl or two at my first shoot I quickly made it a policy to ask about flash beforehand. Interestingly, in that first shoot I asked between sets and got the okay, after which ... no more scowls.
However, you are right that in most cases a flash ruins the shot. Unfortunately, the camera I now have is the only one I'll have for a while. And, no mirror-lock... booo. So, I have been researching and reading on ways to 'use ambient light' and use software to minimize noise.