The Tale of Two Wasteland Version has been released:
https://www.nexusmods.com/newvegas/mods/68030


Note the Fo3 version is not supported and has not been updated since 2020. As such, much of the content in the TTW version is not present in the Fo3 version.
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DESCRIPTION
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Rebuild the Capital is focused on expanding the Brotherhood of Steel and their role in the wasteland following the events of Broken Steel. Rather than sit on the sidelines after establishing dominance in the wasteland, the Brotherhood can spread across the Capital Wasteland under the guidance of the player. The Brotherhood can bring settlements under its protection and can build military installations in wastes and the D.C. ruins. The player can help rebuild Grayditch, establish more Brotherhood patrols, and turn Adam's Air Force Base into an impressive base for the Brotherhood of Steel. The mod also adds a large assortment of weapons, armors, perks, and NPCs. The mod also features several new quests that deal with reunifying (or destroying) the Outcasts, finishing off the last of the Enclave, the relationship between Ghouls and the Brotherhood, and continuing the fight against the Super Mutant threat. Lastly, Rebuild the Capital includes a new recruitment system that allows you to recruit combat squads that will accompany you on your exploits. Overall, this mod is not meant to overhaul the game, but rather to serve as a companion piece should anyone return to Fallout 3. Lastly, this mod was inspired by mods like Mothership Zeta Crew and other great mods that keep breathing life into this very old game.
 
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GETTING STARTED
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I would recommend that you start a new game for this mod due to the many changes it makes, but it's not required. You can access the bulk of the mod's content after completing the quest "Who Dares Wins" featured in the Broken Steel DLC. After completing the quest (without destroying the Citadel), speak to Elder Lyons about planning the future of the Brotherhood. You will then complete two short quests before you are moved to Adam's Air Force Base where you can access to the majority of the mod's features.
 
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CIVILIAN AND MILITARY INVESTMENTS
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A big part of this mod is "investing" in settlements and military bases. Investing settlements brings in taxes that provide revenue for future in investments. These taxes can also be used to invest in the military expansion of the Brotherhood. The more you invest in the military, the more Brotherhood campaigns you unlock. In order to invest in most settlements or military structures, you need to complete a related quest. For example, to invest in Megaton, you need first to defuse the town’s bomb. To invest in the Lincoln Memorial, you must first complete the quest “Head of State.” And so on.

Here is guide that can be read online:
https://pastebin.com/EHaZusSH
 
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CAMPAIGNS
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A majority of the mod’s quests are handled through Brotherhood campaigns. After you have invested enough in the Brotherhood’s military capabilities, you will start to unlock campaigns. The more you invest in the military, the more campaigns you will unlock. These campaigns focus on fighting the Brotherhoods enemies like the Enclave, various raiders, or Super Mutants.
 
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RECRUITMENT SYSTEM
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After the Brotherhood take’s Adam’s Airforce Base, you can access a terminal that will allow you to recruit small squads of soldiers that will follow you into battle. The farther you progress in the mod through civilian investments, military upgrades, and Brotherhood campaigns, the wider a variety of troops you can unlock for recruitment. For example, allying with the Regulators will allow you to recruit a team regulators that will accompany you across the wastes.
 
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LORE
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This mod attempts to be as respectful to the lore as possible while also allowing for a wide variety of player choice. This mod is not meant to be a prequel to Fallout 4, but you can attempt to carve out a Brotherhood that closely resembles the one that appears in the Commonwealth. The Brotherhood can become as progressive or as traditional as you want.
 
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INSTALL
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Rebuild the Capital requires all Fallout DLCs and requires that FOSE be installed.
In order to install the mod you can either:
A: Use any mod manager of your choice and extract as you would any other mod.
B: Extract the zipped folder and empty its contents into the Data folder located in your Fallout 3 directory.
 
JUST BE SURE THAT ARCHIVE INVALIDATION IS ACTIVATED or else the expected texture bugs will appear with armors this mod adds.


NOTE ON UPDATING:
    1. Before updating, be sure to travel to a location that is not affected by Rebuild the Capital. I would recommend Craterside Supply.
    2. Save your game then remove old version and hotfixes, and then install the new version of the mod.
    3. When you reload your game, you should receive a message that says "Rebuild the Capital Updated!"
 
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FUTURE PLANS
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There is a lot more planned for this mod although who knows how far away:
-Allow the player to expand the reach of the Brotherhood to areas added by the DLC
-Expand the number of civilian and military investments.
-Add more Brotherhood Campaigns
-Rework the recruitment system so that it closely resembles something like the Enclave Commander mod although a bit more balanced.
-Mod patches for  other mods (Feel free to make your own mod patches)
 
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BUGS AND OTHER KNOWN ISSUES
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-When taking the Vertibird to and from Adam’s Air Force Base, anyone following you may not appear. Entering a new cell or waiting an hour will cause them to appear and resume following you.
-Some weapons may have odd reload animations simply due to the restrictions will Fallout 3.
-There are probably a lot of grammar mistakes and misspelling throughout the mod given the large amount of text added through NPC dialogue, terminal descriptions, messages, and other things.
-After you have invested in the Pitt, do not fast travel when in the Pitt's Steelyard. Doing so will take you to the Pitt that does not have the Brotherhood.  Simply travel back to the wastleland using the cart and when you return to the Pitt, the world space should be back to normal. If you see a Brotherhood symbol in the bottom left hand corner of your map, then it is safe to fast travel.
-If your game crashes when in the steel mill during the Second Scourge, simply use the console command killall when you enter.
-Wernher has a habit of not staying in the Pitt after he has won, and sometimes ends up spawning at random places. I think this is a vanilla bug.

-There may be other bugs that I am unaware of. Please feel free to report them.
 
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CREDITS
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This mod would not be possible without the many wonderful mods that have been made over the past decade.
 
Mothership Zeta Crew (No resources used from the mod just an inspiration)
https://www.nexusmods.com/fallout3/mods/8747
 
tailor maid
https://www.nexusmods.com/fallout3/mods/18921/
 
classic fallout weapons
https://www.nexusmods.com/fallout3/mods/2307?tab=files
 
classic enclave power armor
https://www.nexusmods.com/fallout3/mods/4641?tab=files
 
20th century weapons
http://modsreloaded.com/19th-and-20th-century-weapons
 
brotherhood environment suit
https://www.nexusmods.com/fallout3/mods/15174?tab=files
 
brotherhood enclave armor
https://www.nexusmods.com/fallout3/mods/20370?tab=description
 
scavanger armor
https://www.nexusmods.com/fallout3/mods/10228?tab=files
 
full leather jacket
https://www.nexusmods.com/fallout3/mods/10206/?tab=image
 
Mounted Heads - A Taxidermist Resource
https://www.nexusmods.com/fallout3/mods/20828?tab=images
 
neunens axes v2
https://www.nexusmods.com/fallout3/mods/5105?tab=description
 
Pip Boy Icons Modders Resource
https://www.nexusmods.com/fallout3/mods/11515/?tab=description
 
T3T Icon Resource
https://www.nexusmods.com/newvegas/mods/49636/?tab=description
 
Mothership zeta crew addon
https://www.nexusmods.com/fallout3/mods/17403?tab=files
 
Creature Resources and Mods
https://www.nexusmods.com/fallout3/mods/13690?tab=description
 
MP5 SD Special Forces SAS Gas Mask
https://www.nexusmods.com/fallout3/mods/4698?tab=files
 
Dogmeat and Other Textures
https://www.nexusmods.com/fallout3/mods/8179?tab=description
 
Candle Modders Resource
https://www.nexusmods.com/fallout3/mods/9349?tab=files
 
various meshes resources
https://www.nexusmods.com/fallout3/mods/22533?tab=files
 
BetterMuseum of American History
https://www.nexusmods.com/fallout3/mods/10983?tab=description
 
Assault Rifle Variants-Modders Resource
https://www.nexusmods.com/fallout3/mods/18501?tab=description
 
Classic HK L30 Gatling Laser
https://www.nexusmods.com/fallout3/mods/4685

Army Of Two Ballistic Mask
https://www.nexusmods.com/fallout3/mods/11087

Classic Combat Shotgun
https://www.nexusmods.com/fallout3/mods/3827?tab=description

Tribal T-51b Power Armor Modders Resource
https://www.nexusmods.com/fallout3/mods/21270?tab=description