Still thinking about that Maritime Campaign.
Question 1 for myself--do I want to allow firearms? I've been imagining more of a standard D&D type game, but with classical pirates and Captain Nemo & the Nautilus as potential parts of the campaign, as well as a potential Chinese/Asian realm, black powder weapons may be appropriate in some respects, and completely inappropriate in others.
While there are some simple black powder personal firearm rulse out there (GW4 and d20 Past immediately spring to mind, and I know there are others), I don't know if I'd want to have to invent rules for ship-mounted cannon. Seems like a hassle. I'll probably just stick to normal D&D weapons and Captain Jack Sparrow will just have to carry around a crossbow with one bolt in it that he's saving for Barbossa.
Question 2--do I want to have a mystical secondary realm? Something that can only be entered through maelstroms, whirlpools, enchanted fog banks, etc? Add a bit of planar travel, even if it's only to an 'alternate prime' of sorts? I'm thinking yes on this one. It'd be a place where I can really throw out the stops on the weirdness levels.
Question 3--do I want to make up a bunch of new fantasy realms for the mainland coastal areas on my maps that are basically just pastiches of real world historical nations but with different and funny names, or do I just want to say screw it and go with real world names for the areas? Having the Greece analog be Achaea, the Norse analog Thule or Midgard, the Chinese analog Cathay, etc. may be easier in the long run.