Also the fact that you need a province in the CoTs area to be able to use the protect trade will make nations more eager to monopolize an entire CoTs area or atleast every coastal province so they do not have to compete in a "protect trade" naval game. I imagine the trade system wont be as much who got which CoT but more who has a province in the CoTs area and which of those has a costal province and the best navy to channel the trade into their pockets.
This would also make it way more important to centralize your colonies and could lead to more historical colonisation patterns i hope.
This would also make it way more important to centralize your colonies and could lead to more historical colonisation patterns i hope.