I'm sure something like this has probably been said before, but I'm not gonna read through 30 pages for it.
Instead of the game being decided by winning or losing rounds, the team should have a certain number of points they need to reach to win the game.
The robbers team spawn (wherever) and have a specific place to rob (bank, malibu, pizza place etc) They make their way to the target building and have to stay there for a set amount of time (to complete the robbery) then escape with the money to a hideout. No bonus for killing cops. After escape (or failure) they are given a new place to rob. Success gives them maybe 50 points.
The police naturally start at a police station, and have to get to the place being robbed, and deal with the robbers. If possible it would be good to have an arrest feature. I thought of this happening in a couple of ways. One way would be to just knock the robber on the ground then arrest him which renders him immobile (though he can be released by another robber). Another way (though possibly completely unfeasible) would be, when a robber is arrested his player becomes AI and follows the cop around and gets into the car with them. With this method, the cops would have to take the robbers to the jail in the police station (near malibu club... whatever the area is called) making it a lot tougher for the cops to do it. Again, another robber can release them.
A cop killing a robber with a gun would give the police maybe 10 points. Using a weapon such as a nightstick gives say 25, and successful arrest gives 50. This should probably be altered according to the max score.
EDIT - ok so there's a similar (albeit less detailed) idea on the 1st page. Oh well