I wouldn't mind seeing a more "regular" fallout mod. Though it'd probably make more sense to play as Wastelanders rather than Brotherhood or Vault Dwellers (or some analogous faction(s).)
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The reason to use Vault Dwellers or an equivalent is because any weapons a civ has access to normally is available through metalsmithing/bowyer reactions. Limiting Vault Dwellers to non-firearms and providing custom reactions for the player is a lot more reasonable than either stripping all firearms from wastelanders/BoS/etc civs that are playable or letting the player make assault rifles and belts of ammunition from wood.
You misunderstand. I mean making them (or tribals,) the main playable faction, not an option. Honestly it's one of those situations where if you have to do that, then only having one playable civ is the best option.
Wastelanders and tribals may only have three working guns between ten people (Jackals are a good example in a fallout game - the Nipton Road Rest Stop Ambush has with AWOP installed, a whopping 4 ranged fighters out of a group of 11 people. Without it there's one guy with a handgun or repeater out of a group of five) Crossbows and bows would be reasonably common, either hand-made or scavenged, and melee or bow/crossbow combat would be a primary option for them simply because they may not have access to firearms or ammunition for them. They can also be expected to have some basic understanding of scavenging, food prep, foraging, and possibly farming, hunting, or herding, gained by living topside and fending for themselves.
Another good example are the Dead Horses, who often still rely on melee combat simply because there may not be enough weapons/ammo to go around.
In contrast, Vault Dwellers and Brotherhood can be expected to be better armed and educated, but not necessarily the best equipped to survive - The Brotherhood for instance is strongly implied to not produce its own food, trading either protection or arms and munitions for it instead. Vault Dwellers meanwhile would be in the business of building new cities and setting up farms, not digging new bunkers, and would thus transition to wastelanders themselves over time in everything but name.
So the compromise is in my opinion at least, either play as wastelanders because they simply can't always have access to modern weapons, or perhaps tribals, who have very few of them most of the time anyway barring exceptional cases like the Boomers and White Legs.