Is your feature request related to a problem? Please describe.
Since the Nether is "FULL" it is very hard to see player activity even with some of the example transparent options already in BlueMap. A solution similar to the overviewer Nether Primitive nether render would be ideal and may also be useful for other custom game types where the dimension is full to the top of the world.
Describe the solution you'd like
Have a render option that removes or makes transparent ALL blocks connected to the ceiling.