You can change clearance to that none will access the base.
I prefer that option which is reversible, than pure destruction, with no way to come back.
About upgrade, it could be interesting, altough, it could be nice, sometimes, to come back in your old trapper camp, after been used to the outpost, next to it.
This old base is like an old friend that you didn't visited often.
I hope there would be no destruction. (it is not a shared opinion, just that i got fond of this cession bases)