Here is my suggestion/ideas;
I actually like the layout and the weapon placement however I haven't played a duel in it yet to see it in action. From a quick walk through I feel your top area is just too high, the lifts while like the King BFG lift raise quick but it just feels like you could half the height and still achieve everything you are going for. Also the BFG instant death trap takes away from the central fight area. Instead of having an open area it is all blocked off by the raised wall which leads to a hallway in the open. I think just the two ways to deny the BFG grab are enough, you could get rid of the pit entirely and allow action to flow through it. I also wonder if you could just place the RL where the plasma is as it seems to be a very good weapon for the map while the plasma is relatively weak.
I would also suggest adding some ammo and maybe a few stims in different areas.