imagine an opening cutscene of a innocent young married couple strolling down the streets at night when they witness a major drug-deal. the wife is shot by a gang member, the husband who carries a pistol (only for proctection) shoots and kills one of the gang-members and then lies over his dying wife as the police come and arrest him. it later shows him in prison writing a letter (with the movie voice-over thing aswell) which reads:
"its true what they say, prison does change a man. normally its changes the guilty into the innocent but for me it was the opposite. its been four years now since that fateful night, those four years have taught me how to survive amongst criminals and have left me yurning for revenge......."
he is interupted by the warden who says there is a vistor to see him. the vistor(unknown to prisoner) asks "were you the only witness of that major deal four years ago". he relucantly replies "yes". the vistor says "thats all i need to know" and leaves the prison. the prisoner is later tranfered to another prison and as the prison bus reaches the free-way an unknown sniper shoots the driver resulting in the bus flipping over. a car pulls up and drives off with the prisoner. the driver turns out to be the mysterious vistor. he says "everyone wants you dead execpt me. i need you to help me take down the [insert name of gangs]. i want all that cash, and your the only man who can help me." he suddenly screams "oh shit!" and shoots at two men on motor cycles. "these guys want you dead, take the wheel, drive to [insert street name] ive got bought you a place where you can lay-low (a blip shows up on the map and you are placed straight into the action where the cut-scene left-off). when you arrive it gives you the usual tutorail and he says "sleep.ill pick you up tommorrow; ill get you some food,threads and a cell-phone." you then meet him and you are given a tutorial of the shops in-game.
As the story progresses you begin to get less involved in the revenge and more involved in greed. this would create the opportunity for more things to buy. it would also work well with ,new major on the block's idea.
other idea: buying and customizing cars and boats and heli's. ie you buy a car and itll respawn at your desired safehouse time and time again. safehouses could be upgraded with more parking spaces and helipads (certain safehouses may have a jetty). you could customize boats and helis by adding fixed weapons(driver) and mounted weapons for passengers (hired goons).