So, one thing that New Vegas makes very clear is that the glory days of the Brotherhood of Steel are long behind it. They can no longer rely on superior technology alone. They got their asses kicked up and down the Colorado by the NCR, and the New Vegas cell has spent the past seven years hiding in a hole in the ground, hoping all their problems will just go away. They're stuck in the past, obsessed with tradition, and unable to change. Despite Veronica's best efforts, it's clear that the Brotherhood of Steel is effectively doomed.
The Capital Wasteland cell, meanwhile, is flourishing. They've recovered piles and piles of pre-War technology, have actually assembled a large army, and command the loyalty of the populace. Like it or not, if the Brotherhood of Steel has a future, it's going to be in the Capital Wasteland. So it's worthwhile to take a look at the Capital Wasteland cell, examine what they're doing, and see what they could develop into, given the attention they deserve.
The Brotherhood of Steel is based on medieval knightly military orders, such as the Knights Templar or the Knights Hospitaller. They are a monastic society that live in their own fortresses and combine religious and military lifestyles. They are led by the greatest knights and the wisest priests. They are an elite, enclosed society, who generally do not accept outsiders. And, of course, they wear big shiny armor. The historical military orders were founded for the purposes of carrying out the Crusades. While their primary purpose was to assist the Christian forces in fighting Muslims, they also naturally acquired territory of their own as part of the process, either conquering it from Muslims or purchasing it from fellow Crusaders. For the most part, this was limited to their own strongholds, much like the bunkers preferred by the Brotherhood of Steel.
The Crusades ultimately ended in a decisive Muslim victory, and with the end of the Crusades came the effective end of most of the military orders. There were two exceptions. While most of the orders held territory only in the Holy Land itself, others had been granted land outside it, or had conquered it in other Crusades against other enemies of the faith. The Knights Hospitaller conquered and ruled the island of Rhodes for over two hundred years before losing it to the Ottoman Empire in the 17th century, after which the King of Spain granted them rulership of the island of Malta, an arrangement that ended only in the island's capture by Napoleon in 1798.
The other exception has a little more relevance to Fallout.
The Capital Wasteland Brotherhood is Prussia.
The Kingdom of Prussia, what would become the nucleus of the German Empire, has its origins in the conquest of Prussia by the Teutonic Knights in the 13th century. While other conquests by military orders would ultimately fade away, the Teutonic Order's conquest stuck. Initially ruling as a "monastic state" similar to the arrangement in Malta, they eventually secularized and became first the Duchy, then the Kingdom of Prussia. While Prussia's military prowess wavered over the years, its origins as a military order clearly influenced its culture. In the 18th century, Prussia was often called "An army with a state" for the size of its standing army, which seemed to encompass its entire society. As Prussia became the power center around which the German Empire formed, this militant culture became the source of the stereotypical orderly, discipline-obsessed German.
The Capital Wasteland Brotherhood is in a similar position to the early Teutonic Knights. They are, in effect, an army faced with the very problem of having acquired a state. They are the only authority in the Capital and the strongest military power in the region, with a successful policy of integration that, in combination, will almost certainly lead them to grow. As they grow, and as they continue to integrate more "locals" into their command structure, they will have to abandon many of their old traditions. Arthur Maxson will probably stay in the Capital, even if Lost Hills is still around to return to when he comes of age, and it seems possible that the pseudo-monarchy of the Maxson dynasty will continue in the Capital. Eventually, the Brotherhood will "secularize" as the old traditions fade away, and the Maxsons will find themselves the de facto monarchs of a highly militant state.
That, in particular, could have some very interesting implications.