There will be many who want to play "solo" without a group, or even want to strike out as a small group of friends. And, as with any game funds are an issue. Funding the servers/staff. Right now the game does not look suited for "solo play" Would this idea of a "Hermit" monument allow for that?
Each suggested monument would come with different protections, more for the hermit, lessening as monument size increased. The smaller monument would be easier to put up, and cover a much smaller area. Why not make them upgradeable too if you have more who want to join in.
Your benefits for raiding or sieging a smaller monument would be less and the occupants would loose less.
They'd be locked into the regions tax system or maybe, whomever raided them last would get their automatic tax... making such places of some value to neighboring larger groups.
*Came up with this idea a few minutes ago, obviously need flushing out. The current monument system is upgradeable, and increases members cap as it does so, maybe this concept could be incorporated with out too much trouble