I have never come across a UPS on a stack (although I can imagine a thoughtfully selected one might look good at the base of the stack - it would certainly add some heft
, as well).
Surely (modern) theatres already have "emergency" circuits - and even UPS outlets - already available?
Anyway, the first thing to be considered must be sizing (capacity); how big - in kVA terms - would the UPS need to be?
A good exercise in Cost-Benefit Analysis, no doubt.
Lastly (and off the top of my head), could we be sure that digital equipment (camera, recorder, display etc.
) would be tolerant of the less-than-perfect (non-sinusoidal) output from a UPS?
.pdf may be useful (no mention of UPS).