Freeroam would be so much better if we have factions, say law enforcement and two gangs to choose from. Then you would have an instant connection in a random session with people in your faction, and also conflict between the three factions. Territory could be controlled by completing objectives, maybe spray painting gang tags, or for police cleaning/painting over them. Or maybe clearing out the faction NPC's from an area and taking a building or capturing a flag or something like that. People could have the choice to join or stay neutral.
This sounds way too much like APB: Reloaded.
What's too much? Many games have similar themes in them, especially when the genres are so closely related.
I think APB only has cops and criminals, not gangs. Also in APB criminals ram raid shops and steal TVs then the cops arrest them pretty much. It is a great game though (as it lets you be a cop which is really cool) but this would be quite different.
In GTA:O gangs could do drug deals, drive-bys, gang members could burgle houses, rob stores, then the cops get the call on their radio and chase, fight, arrest them etc. Every time a criminal player gets a wanted level the player cops get radio calls.