I say that a Rags to Riches game is a bit blase. I like the idea in GTA4 about revenge, but I think it would be better served with a larger dose of urgency. I think the object of your vendetta should be revealed early, then you miss the chance to kill them. Then they could spend the rest of the game taunting you and throwing roadblocks your way as they unravel into a paranoid mess when you keep refusing to die. This can be compounded by initially being part of a small group that all want revenge and/or power, but they all eventually turn on you.