An average librarian probably more intimating than Al D'Arco. I didn't read his book but he was called the professor for a reason- ie that he was a joke that appointed boss only because Gas and Vic decided he was too weak to be an actual threat to runaway with the family.
I'm not as knowledgeable about the mafia as some of the people here but Salvatore Avellino strikes me as a guy that could have made a decent boss. Even Bowat. Yay? Nay?