Turnbull, I agree with all that you say about what would have taken place if Michael had been killed in Italy. But I also believe that some how, in some way, Don Vito would have avenged the killing of Michael and that both Barzini & Tattaglia would have been taken out.
At that stage of the game,Vito knew he wasn't going to be around long,and Fredo was useless as far as keeping the Family active.
I agree with Turnbull that the best move was to let Clem and Tess go,either under Barzini or,on, a smaller scale,on their own.
At this point,Vito taking out Barz and Tatt would only serve to kindle a major war that the Corleones could never win,plus it would disrupt Vito's plans to gradually get out of the crime "business" and retire peacefully.
Vito had neither the incentive or firepower to kick the sleeping bears.
