So, I had a brainstorm on my way home from work the other day:
Everyone I know really wants to play a pirate campaign, but the very nature of pirates (being rather on the independent side of things) means there really isn't a ready-made adventure path, campaign, or even really any modules where the players are pirates, and it'd be a ton of effort to write one yourself.
Then I realized that the Kingmaker mechanical framework would make for an awesome pirate/nautical campaign. It's already designed to be sandbox in nature, the mechanics are already very abstract, and there are already at least basically useful rules for most everything you'd want to cover in a pirate campaign.
Thus, I committed to running a pirates campaign using the Kingmaker mechanics after our current Kingmaker campaign is done.
What I'm looking for advice on is what sort of changes could be made / would need to be made to the Kingmaker mechanics to suit a campaign that starts with a single pirate ship and potentially grows up into an entire pirate empire.
Our group doesn't mind a bit of extra complexity, and in fact we've found the Kingmaker rules a little bit too abstract sometimes, so any suggestions are good.
Right now I'm looking at adding a "notoriety" stat to the overall nation stats, which would determine how much effort other nations put into suppressing the pirates. I'm also going to remove roads because they make no sense in a nautical campaign. Obviously claiming territory will have to be restricted to just hexes containing land; it's real hard to claim any significant amount of ocean. The magic item economy will be removed with the focus instead on trade routes (the players' own trade routes as well as the NPC nations trade routes that they can pillage), with profit from trade routes being based on length and possibly on actual goods traded. The buildings available for each city will probably be re-built from the ground up, and I'm thinking of changing the non-city constructions as well.
Also, the mass battle rules will probably have to be seriously overhauled to work with ship-to-ship combat, although I could see each ship being an "army". I'm holding off on even worrying about the mass battle stuff for now, though, because Ultimate Combat will be out long before we're ready to start this campaign and is supposed to have more fleshed-out mass battle rules in it.
Can anyone else think of other changes or additions?