I have been messing around with Diplo and it seems a little thin compared to entrenchment, at least in what it adds to the game. I noticed the stuff with the pirate and immediatly thought hey it would be great if on those days our gaming group gets an odd number we could allow the odd man to play the pirates! Just in general I think this would be a fun game mode plus allow for even more vicious pirates with a human at the helm. they could control the fleet and only have the enemey activate per the bounty board. Maybe even throw in some diplo options for them to negotiate a hit or even payola not to be hit. Maybe even give them a win condition if they accumulate more wealth than 50% of the total income generated by all players during the game. Just the beginnings of my thoughts I am sure the community could add some great ideas.

Also I would really love to see a multiplayer mode in sins where players could co-op a single player. So for instance a 4v4 could be setup as a 1v1 game with 4 players on each side within the game an a process where a team captain could give a player control of ships/planets/structures. Would allow for a much better micro experience within the game, just throw tom a few ships and let him go raiding, throw larry the main fleet while you as team captain handle the econ/planets/tech  and building new ships. There might even be some interesting diplo options in here somewhere.