This was something someone pmed me about, so here's my idea for a new threat!
Lets start off with setting: West Coast, post-Fallout 2. In Fallout 2 you saw bitter tensions and more talked about in the Van Buren concept. The world is much more developed here, but still reconstructing itself. Cities are expanding and the classic problems of today's world are settling back into their original niches of society.
Now, Enter a new threat: The anti-Chosen One, if you will.
I'd like to see a new threat that is small, unorthadoxed compared to previous games, and easily underestimated by the world in general. Something that's out there not with a large army, a new virus, or higher tech and the like, but someone that has...wits, abilities of manipulation, and so forth. I'd like to see a threat that can cause the world to tear itself apart rather than tries to openly strike upon it. A Joker from the Dark Knight, if you will, or that benefactor who says "It would be in your city's best interest to attack the NCR and take over whatever resources they have. You can afford it, it won't cause your state too much harm. Trust me" and so forth. It's a very undeveloped idea, but it's...different and something I think would be interesting.
Overall I just would like to see something that causes a global change in the world provided rather than just "The enclave attacked your village! ohnoz...nobody else is effected, btw." I'd like to see something that very well threatens to turn all that was built up since Fallout 1 and bring it back to wastes and rubble. You're job, whoever your character would be, is to either join this threat, prevent this threat from continuing, or using the mayhem to your advantage and so forth. After all, war is profit and war never changes
We haven't actually seen a way in-game either to prove that it hasn't changed post-apocalypse, after all.