Mr_K: The map looks great, and I thought of an idea for it. Have a roof, but destroy about 60% of it. Leave panels lying on the ground, and have some attached to the girders to make ramps that players can walk up. Basically make it possible to walk around up on a second floor, but make it really complicated to navigate and get up their, and with a lot of space to fall through the floor.
Just an idea though, since it might make the map more indoors, which isn't what you're going for.