First, take a look at the Fallout 1 Map.
http://img2.wikia.nocookie.net/__cb20080524040043/fallout/images/thumb/7/78/FO1_WorldMap.jpg/500px-FO1_WorldMap.jpg
Where are all the locations?
Thing is, that's kind of it.
There were, of course, random encounters, and the locations themselves could take up several cells, and all the combat was turn based, so, the game, with what's seen here, actually took a little time to play.
Don't, however, let the lack of locations fool you. Those locations could take up quite a bit of time to craft properly, and scale to a 1st-person playable size.
Further, I think some of the locations, like Cathedral are locked and can't be found until you get the Water Chip for Vault 13.
A way to work that when building the Boneyard (Los Angeles) would be to allow discovery of Cathedral, but, keep it locked, off limits, or plausibly inaccessible until the right time.
And, hey, you get to build LA. You could have fun with the LaBrae tar pits, bombed out Movie studios, half crazed delusional ghouls that use to be movie stars (Bill Murray played himself in Zombieland), build a wrecked and collapsing Playboy Mansion to tour, visit the major tourist trap spots all over LA, and add in a post apocalyptic population of characters and enemies and side quests.
Possibly look at how the Capital Wasteland was built, as well as New Vegas, and take some design cues from there. You'd have to scale LA down considerably, but, you'd have plenty leeway and creative license to go a little bit crazy on imitating some of it.
With all the "empty" space on the original map, you could assign some of the random encounters from the original game to those areas, and even add locations like some of the more stand-out notable towns.
All the scripts for dialogue are floating around the internet somewheres, I'm sure, and, it'd be interesting if the assets available in the Fallout 4 Creation Kit allow for taking voiced performances, exporting them to a sound mixer, and splicing together your own lines. If not, then, you could fall back to the original text option or find people that will volunteer to do voice acting.
You've several many months until the release of Fallout 4, and then some months more until the Creation Kit. It might be a good time to begin research, play the first game, and start mapping out expansive additions to each location, including vertical which wasn't an option for Fallout 1 and 2.
If you've anything you want to bounce off of me, feel free to message me here, but, there's tons of resources online for the lore, behind the scenes stuff, and other materials, like companion SPECIAL stats, and other things in the wikia alone.