Trade routes?

How about being able to set up trade routes with another player? This could be used as another form of income for those who can't get any forts or don't sell on Market often. It could be use a 'level up' system, and the higher the level, the more money you get back?
I think you could form a trade route with anyone but the route would become stronger with more interaction with the other player. This interaction could be through buying/selling off each other and through letters and private chat. I think it could cost a small injection of money and resources to get the trade route started, then wouldn't need anymore influence, unless you want to improve it. Once it is set up, the trade route could require an hourly person input (to make deliveries on the trade route) which would reduce the main building person input, and the output numbers would increase as the trade route strengthens.
I can't think of anything else at the moment and this was of the top of my head

Any feedback, good or bad, is appreciated.
Thanks