When your brother is dead, your body won't feel pain when you on a killing spree. He will be slaughtering that village until he drop dead period. **** it. He will make all the akatsuki gangbang that village. We already saw what nagato can do!
Itachi will run through the hidden leaf village with his woes XD
Kisame and itachi alone can possibly kratos the whole village , Water Dome plus a couple shark/bullets/kamehas tear most the village apart , Add kakusu/deidara to this and the death rate will rise to levels pain could never replicate lol.
But anyway sasuke wont be killed before he fights itachi as there is none strong enough to take MS Hebi Sasuke along with oro/kabuto lookin out for him.
Sasuke would be able to beat Itachi if that was the case, Orochimaru told Sasuke he has more power in his eyes than Itachi so the way I see it Sasuke 3T>Itachi 3T and Sasuke MS>Itachi MS (talking about mastery of their Sharingan). Sasuke was slightly slower than Itachi but with MS he would be able to predict Itachi's moves better than with his 3T. Sasuke's chakra also increased when he got MS so I see Sasuke at least out lasting Itachi (CM would add senjutsu to Sasuke's jutsus making them stronger so we can see Senjutsu Susanoo like in war arc.
As for Naruto, I see Tsunade sacrificing her life to revive Naruto like how Chiyo revived Gaara when he died for an hour or so. This would cause the village to look for another Hokage which most likely be Jiraiya. Jiraiya didn't want to be Hokage but I see him taking the role so Danzo wouldn't. That also means Sakura wouldn't be trained by Tsunade so she might ask Kakashi to which would be good since he can train her in ninjutsu, taijutsu, and genjutsu.
Great post , with MS , Hebi sasuke's amped with CM2 would push his power to new hights , not to mention that karin noted that MS sasuke's chakra at the summit was already darker/stronger than CM2 , adding these two together plus orochinaru's chakra would push itachi way beyond his limits and would most likely hav gained EMS right after the battle.
-Tsunade reviving naruto would fit perfectly and jiraiya becomin hokage would hav given a nice spin to the story.