Okay the suggestion here is like to sign treaty's, give the Kage's the authority to appoint one person as the treaty negotiator, but treaty's are not the only thing, this also applies to war time, say a village wins a war, the defeated village would become basically a "colony" off of the winning village basically the losing village becomes ninja of the winning village and the village leader of the losing village is taken out of power, now there is always the rebellion option, where if this group can kill the kage they will win they're land back.