@dch bspwm, herbstwm, patched dwm all have those same possibilities. But how do you represent related children of different trees ? The #Genode letzeinrale is probably the closest thing to what I'm imagining, it manages the trust graph between components. I wonder if they have any plans for making it handle windows as well as the capabilities between components.

I dont even know if XCB can represent a desktop zooming in and out. (not inside the windows, but outside)