Didn't see anything referring to this idea in any of the core or bloats (though, I really only skimmed).
Have each town, outpost or retreat (or any other kind of settlement a race uses) develop a local industry. That is, something that it's good at producing.
For humans, most of the smaller villages and towns should probably have farm production be their primary industry, for export to the larger cities. Another possibility could be mining towns, with forges and the like. Another could be textile production. The bigger cities could have artisans who could turn raw products into finished products. Similar focuses could be implemented for each of the other civs.
The idea would be to make this all highly abstracted during world gen. Warring civilizations could target specific towns who have a particular industry they'd want to disrupt (target mining/foundry-type towns to disrupt weapon and armor production, target farming villages to disrupt food production, etc.) Thieves could target locations that produce finished goods, rather than raw materials.
Likewise, this could have an impact on population migrations, based on what profession a person has. The cities would attract a higher percentage of skilled craftspersons, while costal cities would attract fishermen. Mining towns and foundries would attract miners and smiths, and outlying towns could attract higher numbers of rangers and hunters. Potentially, you could set it up so that the cities attract larger numbers of adventurer types so that, when your adventurer wants to start up a party, he goes to a tavern in a big city and asks around (could the production of people crazy enough to go adventuring be considered an industry?).
I think there's some potential here, and I think I've really only skimmed the surface.