WOW looks like a cool project. I bet those small rooms were intended as pipe chambers when the building was first built. Sounds like you have great ideas for speaker placement. As far as the console is concerned, you might check out Ebay, I've seen several Hauptwerk configured consoles for 2000 2500. They are usually gutted Allens. adding MIDI to your existing console is an expensive challenge. especially since it doesn't have AGO pedals.