Ok Im doing it more clear.
There is a subtractive geometry in a famous editors out there, they help so much.
Here you can see. I want go down into the ground physics collision solid,
A subtract geometry box would let me go in, using less complex physics polygons. It's just a feature request that would be great for us .
Technically if this is possible like in BSP based levels, would be great. We would lift a wall and set a Subtractive cube to have a Window.