I'm interested in this idea, especially receiving letter of marques to gain privateer status with a certain Nation. It is my opinion that ports of other nations should be open to traders of other nations so long as the diplomatic status of the countries are friendly at the time of entering port. A man-o'war should never be able to enter the port of another nation, friendly or not. An individual sailing in an commerce vessel should be granted entry however. This could also open up the idea of alliances/relations based upon economic reasons instead of just constant warmongering.