I too tend to believe Vito “would have uprooted” - the clean Michael, a war hero who's never been busted for the rackets – to “take over the Corleone crime empire”

Vito playing weak! would have still planned all the dirty work - killing of Moe Greene, the baptism murders - for Michael “I never wanted this for you” son to carry out or perhaps Vito carries out the murders himself

The Corleones were in full strength with Clemenza, Rocco, Neri, Cicci and even Tessio all on board but Vito would still need a heir

Vito's “goal” of 'legitimacy' thus placing the impossible, unrealistic burden of Michael's “obsession” to become 'legitimate'

I am not sure about Carlo though
Would the always 'nice guy' Vito make his daughter Connie a widow even though “You [Carlo] have to answer for Santino”