Getting back on topic - its an interesting idea and for players who have been around for awhile, it gives them a new goal to work towards - but a few questions
would this be port based - i would think so
also, is there an option to get nations involved here as well - possibly gaining trust faster when trading in a port owned by the same nation as the trader - or conversely, losing trust in a port if you hostility points with the nation who owns the ports exceeds a certain level - if true diplomacy gets implemented this feature could then be expanded into that as well