by Crippen » Fri Sep 28, 2012 2:34 pm
My advice in this area would be applicable, really, to any system. Figure out what the dominating characteristic of a particular region is, and a few ways the PCs could manipulate it.
So, for example, in an area of slums filled with poor people and occasionally patrolled by the controlling gang, you could either have the PCs spend the time talking the people into jumping the rival gang, have the PCs jump enough patrols to wrest control of the region, or maybe have them set enough traps on regular patrol routes that the area. In an area where a rival gang is manufacturing chemical weapons, capturing the abandoned warehouse they're using to manufacture them would be another goal. They could also somehow bring the cops down on a territory, or spark a fight between two other rival gangs to distract from a territory they want, or something.
Then, figure out about how many of these territories you want them to be able to gain in a day, week, or month based on how long you expect the task to take. Then, depending on the rate at which you anticipate the heroes to be able to capture territory, set a rate at which the rival gangs capture territory. Also, for savvy PCs who think to use informants, maybe give the PCs the occasional tip to give them the chance to defend a critical location for free (without spending time).
I would define the rate at which rival gangs acquire territory as a function of how much territory the PCs control to represent that it can be harder to control a larger amount of territory. (Either that, or ramp up the difficulty of taking territory from gangs with not much to defend harder.) So, for example, in a city in which there are 25 territories, if the PCs can capture up to 3 territories per time period and you want them to control no more than 15 territories but don't want them dropping too far below 5, you could define the territory capture function of the rival gangs as
C(T)=[1+T/6], rounded down
where C is the function of how many territories are captured by rival gangs, and T is the number of territories the PCs control.
You could also work dice into it, for 1dX, where X is 1+T/5.
This means that, on average,
For T<5, they lose 1 territory per time period.
For 4<T<10, they lose 1.5 territories per time period.
For 9<T<15, they lose 2 territories per time period.
That's getting pretty complicated, though. I'd just figure out how large of a territory you think it's possible for them to maintain based on the amount of success they're having. If they're doing gangbusters, you could probably have them controlling 80% of a city and within striking distance of rival gangs' headquarters for a chance at uncontested control for a time. Moderate success, 50-60%, low success, 20-30%, and utter failure, 5-10%.