This isn't a bad idea; however, as discussed in some other recent posts - the liklihood for such a thing to be around is low due to the technical limitations of how players will interact on the game world map. Also, should it be true (which it seems like it is) that players cannot be attacked while they are logged off, a regional owner is likely to simply log off to consolidate the regions that he conquers. You know, assuming someone is to abuse it.
Not a bad idea though, regardless. :P