There are lots of old concert halls in various states of disrepair all over Europe and North America, but this one has much more character than most. The furnishings are rather shabby but the seats are very comfortable and retain the original reclining plates from the 1920s (? a guess). The walls could do with some attention and the orchestra pit looks as though nobody has been down there for a few decades. Also its very cold, I couldn't see any heating system.
But the place has class and the acoustics are superb. I would leave it exactly as it is, although I would definitely swap the security staff for something slightly higher up the evolutionary scale (they are cretinous bullies).