How about we back to playing one protagonist but we play him at different ages. The first part of the game will start ten years ago and the protagonist is a young man in his early 20s barely out of his teens. Him and his crew go around committing crimes like fighting rival gangs, drug dealing and robbing people. They get the idea to rob a bank and everything goes wrong. They end up getting arrested and one of your crew snitches in you to get a light sentence and you end up doing a ten year bid.
The second part of the game will be your character getting out of prison in his 30s looking much different than how he was early on and he is out for revenge. The guy who put you away is now some community leader who acts like a goody two shoes who has turned his life around but in reality he is just as crooked as ever. He is even rich by releasing some book and how he reformed himself but he is involved with the people you used to have beef with.
You and the surviving crew plus some new people start rebuilding the crew by doing crimes like drug dealing which would be mission based and a side mission as well and start attacking your rival gangs plus you start doing heists for the big money.
In the end you hatch a plan to rob and kill the guy who set you up and when you have to fight tooth and nail at his mansion to get to him and you get his mansion plus all the cars he owns after you take him out. The last mission will be a major score.