The \"territorial radius\" idea might work for me if you could build fences or walls surrounding your house/guild hall/castle. The larger the building, the larger an area you could confine within the walls/fences. For a small house, it might be just a small yard or garden area. For a guild hall, it might house an outdoor training area or animal pens. For a large house or castle, you could end up with a sizable amount of real estate.
I think that the structure itself should be accessible only to its owners and completely inviolable, so that it can safely be used as a safe house or storage area. As far as the \"yard\" goes, it could be made restricted, or open, or open but designated as a PvP area.
Of course, as you pointed out, this again brings up the concept of PvP, which has been debated over and over again. For the record, I am in favor of PvP in designated areas (certain parts of the Arena, private enclaves, perhaps certain parts of the wilderness). As long as there is nothing in-game which requires a character to enter those areas (I\'m thinking quests here), then there should not be a problem; those who don\'t want PvP can avoid them and pretend they don\'t exist. That is most likely what I would do myself.
