What might be fun to be able to do during the in-game combat?
Do you prefer a static obstacles over a moving objects? If not - shall they be controllable by the dueling pair? If static on the other hand - what palette of player movement shall they offer? Trick-jumps opportunities during a duel for example - would you like it?
Another example I’ve seen lately in other game - a player defending an objective had enemies rushing little room he was in, he had killed one of them through a hole in the door(partially destructible environment) but as he had to reload, the last opposing him had rushed the room. At the very moment he was about to kill the defender inside the room, the latter had had shut the door right in enemy’s face consequently pushing the opponent backwards, then finishing reload and killing the bewildered adversary. 
I wonder if tools for community map-makers would allow such interactions, as well as if they are planned for the official maps, yet the topic is mainly about your opinions, about what would you like to see in DB.
Have a good day!