I suggest the following option to a court/government: For a specific port, support a specific nation other than one self. By doing this, the nations influence in that port is added to the supported nations influence for purpose of determining control. So, if nation A has 10 M influence, nation B has 8 M influence and nation C has 3 M influence, nation C could decide to support nation B, giving nation B control over the port. This decision should only be implemented after a vote in the supporting nation.
I think this will make diplomacy and advancing in ones nation more interesting for smaller nations. As it is, only few nations control ports, and the smaller ones have no influence on this. By implementing my suggestion, smaller nations may negotiate with larger ones as to how they use their influence. It will also give an extra dimension to alliances and port control wars.
I realize that I am relatively new to this game, so there may be consequences of this that I do not see yet, but I think this suggestion would make it more interesting to belong to a small nation, instead of changing nationality to one of the larger ones.