Its all fun but - NO!
ok, they warred someone, ok, they`re so big and bad. if the community doesn`t like it, they should declare and kill of that nation. simply making them unable to grab is just way to much.
the idea is interesting and all, but it will again put the community in trance. its already very sleepy on taking actions, now it will slumber even more. all these problems should be taken care in game by action and not by some regulations you can`t defend against