Damn, now I've thrown my mind out of samurai/ninja gear, and into my "dragon sandbox" idea.
Plotted out what I think I'd need to do to get it off the ground.
1. Use my old Maritime Campaign maps. Here's the Maritime Campaign that barely got off the ground a few years back.
2. Name those islands and peninsulas! At least name ones where lairs will be placed, and ports will be located.
3. Place dragon, giant, and other large monster lairs. At least a dozen to start, maybe more. Maps of lairs (some caves, some ruined castles or cities, some in the wilderness, etc.), denizens (the big monster & it's treasure, plus any guardian creatures/traps, and lesser beasts that dwell in conjunction with or in the shadow of the big attraction).
4. Have a list of what sorts of information/help could be found at ports, with some info specific to each port location (sages, libraries, wizards, navigators, heroes retired and active, etc.)
5. Have at least 5 "treasure maps" of varying levels of accuracy for the players to discover (and they should likely start with at least one already).
6. Make sure each lair's treasure hoard contains some Keystone Treasures (famous named items, whether gems/jewelry like Hope Diamonds, or famous magic items like in my Unique Magic Items downloads over there on the sidebar). For hoards that are only coins, have a history of how they got there (lost pirate treasure, cultists sacrificing to the beast, ransoms paid, or whatever).
7. Make a big ol' list of rumors of all of the above. Make sure the players start with a bunch of rumors, not just one or two (one of the problems last time was that I still hadn't developed much, so I didn't have many rumors for the players).
8. Have a few stock ruined cities, mysterious temples, etc. that could be thrown onto unstocked islands, which would provide some clues to other lairs/important locations if they are explored.