I don't consider them mentioning a faction in Chicago counts as them mentioning it in Fallout 3, because any real Fallout Tactics faction would have been discovered far west of Chicago, with Chicago being the very outskirts, the barren edge of any possible Brotherhood territory as far as humanly possible from the core... much further than logically advisable from the core.
It would take a very, very powerful faction, much bigger than either costal Brotherhood of Steel to still hold relevant control in Chicago... And well... if they were that big and powerful and spread from Cheyenne Mountain to Chicago... then I'm pretty sure Lyons would have seen them while cutting straight through the center of their territory.
So any faction in Chicago is only connected to Fallout Tactics in bloodline and armor and nothing else. Based on the research I have done, if Bethesda picks up Chicago as a project, I would bet my money on it being Enclave town.
And my use of the word 'lame' was more to make a point about the simple answer usually being the right one as opposed to the flashy answer with a dozen different things that could go wrong. In my personal opinion simple is good, simple is a much better foundation for building a good story.
The quickest way from point A to point B is a straight line.
So, in my mod the story of the so called 'Midwest' faction of the Brotherhood of Steel goes something like this.
After the long fight at Vault 0, a valiant effort by Dagger Squad to hold the line, and an unexpected betrayal of the Calculator and return to the Brotherhood by Robobrain Barnakey, it is time for a big decision. Betty, the hero of the Brotherhood of Steel must now decide what becomes of the Calculator. As an initiate in the Brotherhood of Steel it was preached into her head daily that the most important thing in the world is collecting and protecting pre-war technology... and this... this was the most advanced piece of pre-war technology she ever had or ever would see in her life.
But a crazy robot that was build by Vault-Tech, a company that turned its own customers into unknowing test subjects for horrific experimentation. A crazy robot with brains that have atrophied beyond the point of being any good and no longer has any morality or humanity holding it to tell you any sort of truth. A crazy robot that would say anything, in a desperate enough situation it would tell any lie to convince you to not kill it.
Would she really believe this thing, after seeing first hand how Barnakey's mind was twisted and turned around by this very same Calculator. The choice was clear to Betty, it would be nothing short of illogical, irresponsible, and gambling with the lives of the entire Brotherhood of Steel she had sworn her life to protect if she let this mechanical monstrosity survive.
As she stood there, next to the burning circuitry of what was once the demon of the Midwest, she knew beyond any doubt that she had made the right choice. Regretfully however, Simon Barnakey was no longer the man he used to be and could not bear having his loving wife or son see him in his current state. After the destruction of the Calculator, he committed suicide.
So the Brotherhood decides to use Vault 0 as their new base of operations and HQ as they try to rebuild their ranks. Disappointingly, however, even with the technology at their disposal at Cheyenne Mountain, they are unable to restore contact with their Brothers on the west coast.
'Bunker Hill had sent them out east to die', was still the though on the back of their minds as a unanimous vote decided that it wasn't worth the effort to send messengers back west to receive further orders. As the last vote was counted and the crowd cheered, General Dekker stood up and made a surprising nomination. For the first time in the short history of the 'Midwest' faction, they needed to have an Elder to turn to for leadership, and who else but the girl that had just saved them from not only the Beastlords, Reaver Movement, and Gammorin, but the very demon of the Midwest itself, Vault-Tech's Calculator.
Betty becomes the first Elder of the 'Midwest' faction and becomes the start of a matriarch dynasty much similar to the patriarch dynasty of the Maxson family.
The Brotherhood thrives for many years under the wise leadership of Elder Betty. The few remaining citizens of Vault 0 are integrated into the ranks of the Brotherhood, what few robots could be salvaged were refurbished and put to use fighting for the Brotherhood, work on the supermutant sterility cure continued as relations between the mutants and Brotherhood remained healthy, the Deathclaw went back to their homes, and even the Reaver Movement remained peaceful... cautious but peaceful.
One of the robots that was pulled from the wreckage of Cheyenne Mountain started telling Elder Betty of the time he spent working for the Calculator, the time he had fought Gammorin and barely survived, how he had infiltrated and kidnapped the already kidnapped Barnakey from Gammorin, and the respect that he had gained for Barnakey during the time he spent escorting him to Cheyenne Mountain and being his body guard after he became a Robobrain. This particular robot had taken a rocket from Betty to protect Barnakey during the final battle of Vault 0. He had bought the time necessary for Barnakey to notice the locket that Betty carried and re-gain his humanity.
Betty named this robot Cal, after his father, the Calculator. This robot became her personal bodyguard and over the next 40 years of Elder Betty's rule, he rose up the ranks of the Brotherhood to become a Paladin General. Cal is sworn to protect the decedents of Betty long after she dies.
However, this new era of prosperity came with a down side... a down side that would eventually lead to the end of the so called 'Midwest' faction of the Brotherhood of Steel.
The most simple way to put it... people became comfortable.
Betty's daughter became Elder after her mother's death. She was a charismatic and intelligent leader and had no problem keeping things running in a peaceful and prosperous way. She was not however, the warrior her mother was, she didn't spark the flame that made people willing to fight and die for the Brotherhood the way her mother could. She was more of a mayor of the Brotherhood of Steel than a commander.
As time went on, the Brotherhood stationed men all across the Midwest, protecting local settlements, brokering trade pacts with the locals, and building up a new infrastructure for society.
However, ghouls were still loyal to the betterment of ghouls, the supermutants were still loyal to the cure of their sterility, the tribals that joined were still loyal to their towns and families back home, and even the most loyal of Steel blooded Brothers started mingling with locals and falling in love and starting families. Pretty soon many of the Paladins were more concerned with the local concerns of their settlements than the concerns of Brotherhood headquarters. "Why should I leave my family in St. Louis and go risk my life because somebody out in Cheyenne Mountain decided to pick a fight they couldn't handle? What has Cheyenne Mountain ever done for me?"
So in the end, there was no final battle of the 'Midwest' faction of the Brotherhood of Steel. There was no grand last stand, no story to tell, no scorched Earth littered with the bodies of the fallen. There are no graveyards filled with the fallen heroes that made up the Midwest faction.
If you travel across the lonely planes of the Midwest the only signs you will find that the Brotherhood ever did exist is in the laughter of children who can now play safely because their town is protected from Raiders by men with power armor and proper weapons... Men who are descendants of a once mighty faction of the Brotherhood of Steel.
Headquarters is gone, the last Elder is dead, anything even remotely recognizable about the remains of the Calculator has crumbled away. Vault-tech records on Vault 0 were all destroyed long before the bombs fell, and anyone alive to remember the battle that happened that fateful day is long deceased. No glory, no monuments, no lessons learned.
However, there are actually 2 squads that remain in the Midwest. I can continue if anyone is actually interested. If not, I won't waste my time re-typing all of this. In my mod I tell the story through dialogue with different characters and it unfolds over time, so in order to make it readable on a forum like this, I have to re-write it in a more linear format.