I have only just thought of it, but i think that if Ubisoft chooses to use it, they would expand the ideas and make it better.

I have an idea for a game, that will probably be very good, it is basically Assassins Creed IV Black Flag (I don't think it should be an assassins creed game, more like a new game franchise) but online, you play as a pirate or work for a country and you can customize your character how you want (Face customization, tatoos and such), you will be able to own a fleet and make Crews and then people can join your crew, you can take big ships and make them your main ships or buy them, you can also get bounties on you and such, there will be NPC bounty hunters as well as player bounty hunters, the game will revolve around money and lvl, you can upgrade your crew, ship and fleet, if you take a fort or a town (You will need a crew) you will get income, and you can maximize that income by upgrading your crew, you can also upgrade the town and make it more livelier, giving you more money, and you can also make a town by yourself (You will need alot of money and resources) Naval combat will basically be the same as Black Flag, maybe upgraded or expanded, the map will need to be big though, i am also thinking that you can travel to many nations and oceans, you can go to Europe, The Carribeans and The North Atlantic Sea, there will be alot you can do, have i mensioned that you should be able to smuggle and do other stuff like assassinations or trades to earn money? You should also be able to recruit captains for your fleet and maybe also recruit crew for your main ship if you want to, you could pick npc's or players with the best stats to be your crew. I think that such a game would be phenomical.

Also, as a subordinate of a country, you can patrol, take down criminals, guard locations, escort convoys, take cities back from the Pirates and make new cities, and more.
and also maybe merchant or something.

Also, i think that there should only be a few islands and colonies where the players start and then they basically build cities and make the areas more populated, leading to more cities, although there should sometimes be "wipes" or something, since there will be a point where everything has been taken and only the strongest crews and such can get money, then there should be servers so there can be server wipes or something, you gotta start all over again, but it will still be fun.

Oh yeah, you should be able to upgrade nearly everything, your weapons, outfits, ships, cities and even businesses, build businesses, build factories, farms and much more!