Two areas I'm really interested in would be Switzerland and the Mediterranean sea. Switzerland, as of 2010, has its own nuclear bomb shelters built into the alps and room enough for 95% of the Swiss population. Were a nuclear war to occur... would Switzerland's population be unharmed? Would other individuals tried desperately to get in? Would Switzerland have been invaded and its bomb shelters taken over? Or maybe the European Commonwealth forces Switzerland to let others into those shelters? An area so prepared for a nuclear fallout NOW could be very interesting in the fallout world as well, not to mention the alpine setting would be extremely refreshing take when compared to the mostly brown and gray locales of the Capitol Wasteland and Core Region.
Second, I've also been thinking about how, in the fallout world, water is always a BARRIER to the game world, rather than incorporated. Granted, it's not feasable to sail west from California to Japan, but even so... fallout has always been an "inland" setting. What if you had a sea smack dab in the middle of a game area, like, say, the Mediterranean? Not to mention it's right in the middle between Europe and the mid-east, the two combatants in the resource wars? Imagine how the various cultures, islands and coastal peoples would've reacted to a post apocalyptic setting. Rather than raiders, you now have pirates. Rather than the neomedieval organization of the BoS, you have neoclassical settlements taking their cues from Greek and Egyptian and Roman history.
What other areas would you like to see elaborated upon in the fallout setting, and how would you like to see them treated?