The modding community has gone around to adding a lot of missing content back into the game.
There are three mods that restore most of the original game’s cut content:
Nova Arizona will allow the player to access the other half the map that was cut in the original release
Dry Wells will allow the player to access the cut location of Dry wells that is only accessible after completing lonesome road
Long 16 also allows the player to access a cut location that was repackaged as DLC
These three mods together almost triple the size of the games map, and they make the game feel full. Check em out.