I haven't had to time to explore the area to see what would be available to use but since the cops won't be patrolling the area, any cities within that area could be non-governed towns and whatever gang captures and controls that town makes profit as if people lived there and were taxed by the occupying gang. So if another gang wants to attack your town, once they come within a certain radius of the town with illegal weapons, it would be like a town invasion from wasteland servers so you would need to defend your town from the attackers but also could go attack other gang's towns. This would give rebels a way to pvp at different parts of the map away from cities populated with civilians and somewhere they can fight while not having to worry about running into cops patrolling. I think this would give little gangs the opportunity to make money while still having to work for it by defending from other small ones or going after the big gang's towns when they try to take yours. Also to balance the number of players fighting for each gang like turfs you could only have a certain number of gang members in the zone.
TL;DR make gang turfs that cops won't patrol in but gangs can always constantly fight over while the gang holding it makes money over time for holding/defending it