what if caravans allowed others (& your own heros) to purchase items just like the shop in cities?  would be kinda neat to be a ways out from your city and in need of a new weapon/armor when low-and-behold you run across a neighbor's caravan carrying better quality goods than your city had anyway.  You get your goods & they get a cut of the caravans transactions.

and/or if the turn or two your neighbor's caravan stayed at your city you would be able to purchase their equipment without having to travel to their cities (I would love for my allies to be able to by better tech stuff from my caravans)

and/or perhaps you capture one of your enemies caravans, ofcourse you may knock it out or you could reason with the merchant & barter with him for twice the amount (Allowing you to purchase high tech equipment from atleast somewhere if ya & your allies don't have the good stuff)

I think this would prolly be easy to pull off on both games