As Purple said, the war favored the Mist.
Kiri had more 'active' players while in the war, Sunagakure trying to salvage the few remaining active players they had. Even at the time, both my sitter accounts could not find anyone to attack, almost all possible victims being allies; even then, I could only acquire ten Mist kills each.
Now Kiri fighting against Oto wold make for another story, and now there should be no limits if this idea is implemented.
I would have preferred the war to be more roleplaying, i.e., zone fighting and what-not, but that would have ended up badly seeing that multiple factors would play in allowing it to occur.