I was thinking about this while browsing the armor and weapon vendors in-game, and remembered this thread. I checked #14 of the Structures suggestions, and wanted to add my own spin on it:
Perhaps after constructing a blacksmith in a town (not castle or village) a "Royal Smith" building is unlocked. After building the Royal Smith, you can custom order weapons and armor- not just cookie cutter static items, but allow you to tweak the stats. For example, if I'm playing a Villainese light infantryman, I would order a suit of chainmail, sword/shield and a bow. I would have the armor be light (reducing weight decreases armor value; increasing armor value increases cost) and the weapons would be equally nimble. I get tired of traveling from town to town, trolling the markets for useless items.
Now, this wouldn't come cheap and would certainly be end-game type gear, likely for defeating the Legion. Because you could probably fund exceptional armor quickly, perhaps a system could be implemented that each suit of armor is better than the last. For example:
I order my first chainmail tunic for 20,000 denars.
+40 to body armor
+20 leg armor
22 lbs
It works well for a while, then I order my second since my smith sends me a notice that he has developed a more efficient linking method and offers to craft a second suit for 25,000 denars.
+45 to body armor
+22 Leg armor
21 lbs
This would not only provide a (much needed) cash sink, but would make it feel like I'm constantly upgrading my armor past a Lordly Byrnie.