Once again everyone is taking it personal and not keeping it business... Luca was dispensable as he was a soldier and a killer, someone Vito avoided even looking at unless it was absolutely necessary. yes the family would worry if Luca switched sides because that means the old school family loyalty way was over because their biggest muscle was gone, they literally had no power left.. UNTIL Michael the more travelled and trained war hero figured out how to kill the turk. Michael was fond of Clemenza as he was considered more like part of the family, the smart move AMONGST THE EAST COAST ITALIANS was to go with Barzini, Michael had to kill EVERYONE and then run and start all over instead of go with the flow which was what Tessio was planning to do.