Musing about world settings - the sorts of places where I have an idea, and probably no time ever to develop it. (Thinking about this partly because my Sedona setting for modern-day occult/superhero roleplaying keeps sputtering and not getting legs.) The Infinite Archipelago is one such original setting - I have the idea, and have run some short adventures there, but I haven't come up with "this is a campaign, here, let me run it for you".
Another world setting that I thought of, said "this would be so cool", except nothing jumped out at me for how to run adventures in it, was the hybrid modern/Silver-Age-Of-SF solar system: from Mercury to the asteroids, the solar system is what 1952 thought it was (think Lucky Starr); from Jupiter on out, it's what Voyager/Galileo/Cassini have found it to be, with the answers to all current speculation being "yes".
Seems like a really fun place to visit. Except that I can't figure out how to structure a story, or a roleplaying campaign, in it, because a lot of the fun (in my head) comes from exploring it, which you have to limit and leaven with lots of other things that distract from the exploration and tie you to one place for a long time, because in real life exploration gets dull fast.
If I lived in close proximity to my gamer-geek friends I'd try to spend lots of evenings hashing these out and figuring out how to make them interesting. But since I don't, I won't ever. Which is a little sad.