What they need to do is CAP the number of cities any one guild can OWN... I would say 4 being the max # of cities any 1 guild can own.
Then in server 7 Light realm at least a bunch of cities would go unowned because there is only one Guild that can own them. This would have been a good idea before the Guilds started to upgrade and we still had several guilds with active players.
The opinions expressed on this post are my own as a player, not as a Moderator.