That's oversimplifying it a bit, but basically I want a winner-stays-on GS room where guilds who achieve win milestones are rewarded in the same ways that PKers are rewarded for holding towers for hours. In this instance, I'd say 10k wins is the equivalent of traditional towering's 1k hours. Maybe 5k. That isn't up for me to decide.
In terminology that utilizes the current towering system and possibly makes it easier for developers to work with: a tower that is only able to be taken through beating the holding guild in a guild spar.