Each of the POI's that show in distant terrain have a 2d cardboard billboard version of themselves called an imposter (I believe). When you generate the map the game stores those imposters to use for distant terrain and they don't change. No matter which direction you approach a POI from or what changes have been made, that imposter always shows the same distant view of that POI. The imposter isn't voxel itself so it can't be something dynamic where when blocks change for the actual structure it also changes for the imposter. It's just a 2d drawing. There would have to be separate drawn versions of each building to swap in and out depending on the changes-- and how do they anticipate the changes ahead of time to be able to draw them accurately.....?
You would have to create an imposter for your own base (since the developers have no idea what you plan to build to make one for you) once it was completed to the point where you felt it was a good representation and then somehow get the map that was pregenerated before you started playing to accept that imposter and use it at the location of your base for distant terrain. That's a tall order and why it hasn't been done by the developers.
I think your best option is to build warning signs on your approaches that will render first so that you know your walls are coming up next.