Originally Posted by Turnbull
Extract: Sure. Vito, old, in declining health, didn't have long to live,
For all Barzini knew, Vito, could have been dying of the same five shots for twenty years!

My take, it is not quite “co-Donship”
Both Clemenza and Tessio upgrade, their own already separate caporegime to “their own "family" and continue separate as before but independent and a la Michael / Pentangeli

If Tessio had succeeded
Originally Posted by Lana
Clemenza: [fish tank scene]
Quote
Don Corleone you once said that the day would come when Tessio and me could form our own Family
It seems to me the above was the carrot Vito has been dangling and both Clemenza and Tessio seemingly were receptive of the said arrangement / reward

Clemenza and Tessio already had their own territories They could have continued to run their respective Families [like a Corleone!] without Michael on their backs

Michael can still draw the water from their well for muscle and they can certainly present a bill for such services
After all Michael is not a Communist!

Extracts:
Originally Posted by Turnbull
Originally Posted by Evita
We'd discussed in Vito's vs Michael's caporegime thread Barzini can't afford “to wait until Vito died [not knowing when?!]
The longer Barzini waited as Tattaglia said at the Commission meeting “as time goes by and his [Vito's] position becomes stronger....

That was Tattaglia's fear, not Barzini's. Vito successfully played weak after the Commission meeting, and never let on that he knew "It was Barzini all along."
Tattaglia was right!