All of the shinobi in their PTS villages go to war. Their past allies are brought with them, which means..
Sasori returns to the sand
Deidara and Kakazu returns to the earth
Kisame returns to the mist
Itachi returns to Konoha
Nagato and Obito arent factors. They all have their various tailed beasts. All Kages before the current ones are revived (except Hashirama)
Even though I doubt thisll get many replies, let this war begin!