I haven’t tried the steam burrow interface yet, but in previous versions it was trivial to construct an inverted burrow, and they functioned exactly as you describe. You merely had to start by selecting every tile on every z level by just doing a single toggle using two diametrically opposite corners of the map. Then you simply carve the forbidden zone out of that.
This is an interesting workaround. A bit annoying to have to do, especially as in DF 50.x burrows need to be applied layer by layer, but it'd help in most cases.
Still not exactly ideal because there's a big change in how burrows work due to the lack of a Civilian Alert. Without the Alert, dwarves inside a burrow will wait for their current activity/job to finish (including the "No Job" activity) before obeying the burrow, causing a delay that might be problematic.
Granted, this feature would be good to have back regardless of it being a "Reverse" burrow or not.
That's a wall. You want it "pausable", put a door in it.
A door can't be applied to an area where wagons may need to cross.
Walls + door can't make dwarves who are idling inside the area get out immediately.
There are places where it'd be impossible or impractical to build anything, but which are still walkable and it'd be good to stop dwarves from going to.