I created SuperGrid due to lack of usability in BSP. Do you model with SuperGrid or BSP? Hell no! But it definitely helps to cut the corner, when your objective is to create level, game flow on your level and etc. You don’t want to be distracted by visual details or complex modeling features, the goal is creating fun/good-to-play areas with field of view/obstacles/game flow and etc in mind.
Just check out article. is 1st stage of level design and it requires appropriate tools, which is not modeling packages or BSP with improved modeling features.(It should be extended to help level prototyping, don’t get me wrong. I just don’t think that mega-modeling-tool inside UE4 could help in process)