On the one hand, there's the problem of destroying quest givers, and on the other, their isolation.
Making them indestructible isn't a good idea. He might end up in the middle of my base, and what then?
I'm all for making it
difficult to do so, and for being able to track down the perpetrator. That would solve the problem of them being destroyed.
But what about isolation?
Isolation may be a kingdom's tactic, albeit a "bad" one, but only another kingdom or a strong group can counter it. And this is a problem for individuals or small groups.
Banning territorial claims like they do with global resources? It doesn't seem like a good idea.
My english is bEd.