these are some of the things I think would make the game amazing for everyone
1) the ability to create a place for yourself in the game. examples would be being able to start your own town, become its leader, recruit npc and create an army to defend it, possible to attack other "groups" or "factions" on the game map. ruling this place with either good deeds, charisma, and skill, or through brutal fear.
2) more weapon types, more locations, more map. expansions could be easily added as just another map area
3) Randomization. by this I mean having weapons, mobs, npc everything be more random. it seems like within hours of a release like this, everyone knows that if you want the uber gun, you raid the vault34 armory, or walk north out of Vegas to find a fallen ship. It would be infinitely more fun if not everything was certain, forcing people to accept the game as it is, dealing with what happens in the game world instead of planning everything out.
4) six, love, flirting. Im not talking about graphic six or weird nudity, but some erotic elements or just advlt material would be a lot of fun mixed with the dark and dreary aspect of a post apocalyptic world.
these are the main things I think would make a fallout world even better then it already is. feel free to flame me at will, or add your own personal dreams for the future of fallout.