I said it before and i will say it again. GF4 should be done in the flashback mould again, with the rise of Vito Corleone, in the wars with the Irish etc, in the period between GF1 and GF2, coupled with the downward spiral of the family with Vincent as its leader, caught up in the narcotics trade. Robert De Niro as Vito. Andy Garcia as Vincent. Simple. You could call it the rise and fall of the corleone family. It would be great. there are a whole host of actors you could use in the film from nowadays too.