But even with today's codes, I don't think there is anything requiring fire suppression within enclosed timber truss roofs. However, I bet you quite a few other cathedrals are considering it right now.

But as I think about it. It is probably riskier to attempt to make those renovations, rather than keep the roofs as-is. It might be smarter to just make new hi-rise hose trucks. Hell, they can pump concrete up on extended booms via remote control.... why not water with nozzles on the end of a LONG boom?