That is an excellent point, but I wonder if it's even possible to make wholesale changes to these century old buildings to fix the problems that you cite? Space is at a premium backstage, even more so than in the public areas of a theatre and, without increasing the footprint of the building (impossible in most cases), I wonder what could be done. Maybe roofs could be raised and additional floors built up to accommodate, but, if a theatre is protected for historic value, that's probably not an option.
It's such an interesting problem, one that is exacerbated by dealing with old buildings that were designed and built for a bygone era. I know that it would be a horror, but I wonder if the only real solution would be to tear down the old theatres and replace them with modern buildings that would meet current guidelines for safety (and current expectations of comfort) in all respects.