I'd be tempted to leave it just the way it is, run cabling up there if you plan to use it for recording, and control everything remotely from a room down below.
The trouble is, no matter what you do, anything you add to the walls will change the character of the room's sound to a degree. If you have found a great sounding natural space, that can be part of the magic that makes everything you record sound completely unique.
One of my favorite recording locations, ever, was a 200 year old barn that I recorded an ensemble in a few years ago. Given its age, the floors, walls and roof were full of holes, but I think it was precisely that combination of old, dry wood, no insulation, and holes everywhere that made for a really interesting sound.
Anyhow, food for thought
. Best of luck!
Rob Stewart | JustMastering.com