That'd be awesome DLC, in the reigns of the Lost & The Damned, and The Ballad Of Gay Tony. Idk if they'd really make a full game out of just the Five Families, as that'd be pretty limiting. Maybe they can take an HD Vice City approach and have the main character be a mob soldier from one of the Five Families, who gets into a beef and branches out on his own to meet all kinds of nefarious and sometimes completely ridiculous, and mad individuals and make all the moneys. Seriously though, that'd be a pretty awesome GTA game.