Maybe an extra side story for Franklin where he went to repo someone's Infernus, but the guy instead gave Franklin a solid diamond skull as collateral to give him a chance to come up with the money, but then Franklin's skull got stolen.
Franklin reacts: "That ***** took my skull!"
And then you go through 20 missions to get it back.
Isn't that the plot to one of the crappy 50 Cent games?
We all do really dumb things. That's what makes us human.