If i understood well, the Rinnegan can be awaken by having the uchiha and senju power. Naruto has both, because of itachi's crow. Now, i dont know if i got it correctly, but doesnt the rinnegan have the power to revive people? What if Naruto will revive his parents and some awesome ninjas in order to win the war?
And one more thing, if minato will be alive, will be a jinchuuriki, right? He sealed half of kyuubi in him. If he controls that power, and if he uses his old abilities, he wont be able to lose, as well as naruto.
I am sure kishi is planning something big for the war, but why not that?
Why would he insist on minato if he doesnt appear so much in the manga or anime?
Just imagine: the best shinobis ever, saving the world from akatsukis plan.