Map EditorAdded Boundary as a first iteration. The first version is intended to be fence.

I'll probably go with red brick walls and of course green hedges.
This particular one led to some discussion about how fence, hedge or wall should work.
These are all slightly different boundaries.
You might think horses can jump fences so they cross them.
It seems they proved too much of an obstacle for some formed units. Maybe the average cavalry nag isn't much of a jumper and large bodies of men/horse don't do so well with any obstacle.
There is also the issue of the likes of enclosure walls. Often not strong enough to stop a cannon ball so not a fortification really. But if the French could just walk into hougomont then things would have gone rather differently.
At the moment I have fixed "hard coded" settings control who can cross what terrain. This is as well as rates.
It has to be an on off thing because it'll be used real time as you drag a move order "puck" round. No you can't cross one of the pieces of terrain in that direction or yes you can cross all of them.
I'll make this editable per scenario in a new view within scenario editor.
It's then up to you to decide what fences do in a specific scenario stop.