Caesar didn't "introduce the voi". Is this an urban myth that Italians believe? The tu/vous distinction in Romance languages arose in medieval times. Not only did it not exist in Caesar's time, it is absent from the centuries of Imperial-era literature in Latin.
There is a wide literature on Latin forms of address. Eleanor Dickey's monograph published by Oxford University Press is a good survey.
There is a wide literature on Latin forms of address. Eleanor Dickey's monograph published by Oxford University Press is a good survey.