How about something simpler that helps toward the same idea and doesn't introduce any new code: Requisition Smiths.
If you are in a region that has repair smithies, but you wouldn't normally be able to use them (say, you've just sacked an enemy city), you can send your troops out to round up the smiths and force them to work on your equipment. There's a chance you can't find them, a chance your equipment gets sabotaged ("The equipment looks to be in good order, but after you return to camp and begin practicing it breaks in ways you never anticipated. Equipment is now damaged by 5%"), and it burns two hours in addition to the normal repair times. Essentially, it's a military way to accomplish the current use of family gold to buy favours.
