I missed the tunnel at first, but after playing with it, I thought it was a good choice. The tunnels were used more as an escape route rather than a usable part of the map. And if you did ever meet someone in it, it would just be a few shots to kill them, since there would be no where to go.
Now fighting is confined to the lower stairs, the locker room, and the main access tunnel, which still plays fine with several people.