One of the basic design principals seems to be that the NPC lords have to follow the same rules as the player does (with a few cheats i.e. horses required for upgrades). So it seems like since the player can own caravans/workshops, the NPC clans should be owning caravans/workshops. Caravans should be easy to implement. However, with workshops being a limited resource, NPC clans should have their workshops be simulated. Each clan should have a workshop income that is equivalent to their tier level (i.e. Clan tier 5 should have 5 simulated workshops). If we set the average workshop income to 150 denars per day, then 5 * 150 = 750 denars per day (for clan tier 5). These caravans/workshops will give NPC clans a steady income whether they own a fief or not and whether they are at war or not, just as the player should be doing.