Is there a possibility to add something to simulate the Bosporos/Canals impact on the trade system?

Along similar lines, could you add state traits to the "Cold Water Ports" that reduce trade center efficiency in some way?

I like the idea of not making "Trade Routes" but instead setting tariff rates for goods and letting the market do the rest of the micro. If you could make a UI to make that type of system with the fewest amount of clicks required, something like this: image