As you note, Genco and Tom were anomalies because they weren't involved in the muscle end of the business. Nearly all real-life Mob consiglieri came up through the ranks. One of the Gotti tapes played at his last trial has him telling Gravano: "What do you want to be, consigliere or underboss? Whatever makes you feel better."
Ntra la porta tua lu sangu � sparsu, E nun me mporta si ce muoru accisu... E s'iddu muoru e vaju mparadisu Si nun ce truovo a ttia, mancu ce trasu.