Sounds like a reasonable idea. Same intent as making a building and leaving the back off, right?
Thinking some more though: what would you do about the fourth side? So, you'd have a field with 3 fences built onto the base, and then what? If you're going to make a fourth fence on its own separate base, then why not do that with all four fences? That would maximize your versatility, more so than just separating one.
If you were making Normandy bocage, you could build the hedgerows onto the side(s) of a road, or side(s) of a field, but you'd be better off keeping them all separate, so you could have hedges between fields without any road, and use the roads in a village.
So, what things would benefit from some added access or modularity, but are impractical to build if you take it to the extreme? I'm struggling to think of an example of 'natural' feature that is ideal. Although, as Snitchy says, at the very least it will look a bit more "integrated" and natural.
Thanks, now I'm going to be thinking about this all day.
- H8