If Vito had been well enough to take command after the shooting and hospital attempt, I believe he would have tried to find a solution short of all-out war. His prestige, political clout and diplomatic skills--coupled with the fact that the head of the largest and most powerful family in NYC had survived and was in charge--might have forced a solution short of war. I'll guess that he'd have decreed that Sollozzo was to be killed--perhaps by the Tattaglias, since they vouched for him--and that the Tattaglias would have to pay an indemnity to him. But I'm sure Vito would want to limit killing because the more deaths, the more resentment, the more thirst for vengeance.

BTW: I've often posted that tipping the newspapers to Mac's corruption and his relationship with Sol would have provided a nonviolent solution when Vito was out of commission. The police commissioner would have had to provide uniformed protection to Vito in hospital, and would probably have suspended Mac "pending investigation." Sol would be hunted down and either jailed or deported. Vito's political muscle might have been used to either have Mac dismissed from the force, or prosecuted. There would have been no Five Families War of 1946--and no GF Trilogy.