The good news. That plan model on Mongol conquest of China and Qing, the last dynasty of China came from barbarian roots. Conquer the civilized land, keep the barbarians from destroying that civilization, and within 3 generations the blood itself of the horde would be transformed further into civil.
Except the Mongols were very pragmatic when it came down to it. They were the epitome of the barbarian mentality that desires the good things the more civilized had and wanted them without destroying the system that created those things so they could keep making use of it. That was shown from beginning to end where they only wiped out those were very obstinate resisting them while leaving those that didn't resists at all to themselves to ensure their loyalty.
The Mongols wouldn't have been a shadow of themselves without the industry and weaponry they inherited from taking China and would have been just another massive Steppe Confederation in a long line of them that controlled Central Asia since men learned to ride horses.
Both of these things run counter to the spirit of the Legion, especially how Caesar's successors would interpret his intent since he sought to wipe out all preexisting cultures and meld them into the homogeneity of the Legion and looking upon advanced technology as a weakness that would keep them stuck in state they are while actively resisting the melding the Mongol's eagerly undertook.
All of this goes back to it relying upon Caesar, or the Courier as his successor, carrying things so far almost like the Golden Path in the Dune novels the shoulders of one or two men while surrounded by a mass of those who just want excuses to slaughter everyone who isn't them.
++ I presume he modeled his plan on Greco-Roman process but it's the wrong model. Italy and Greece is too small an empire to apply to the continent of North American. You need either the size of India, or China for that. Even Alexander the Great need his father's works to accomplish what he'd done to Greco Roman plus Persia.
Double so given the near non-existent succession laws even into the Byzantine Era that continually created instability and chaos. People can take the Legion at face value and say that's been dealt with by Caesar and things are hunky dory, but the fact that a man like Lanius succeeds says a lot and produces two questions in me.
1: Given his personality and the air he gives off, what do you think he'd have done had he not been chosen to succeed Caesar, especially by someone he felt wasn't as suitable as himself?
2: What if there had been two Lanius' and all the trouble that would have caused, which is what a lot of Rome's old troubles were centered around?
There was a good, flexible and pragmatic system in place that was already tailor made for the people of North America, though the Fallout zaniness does it's best to act like all of that culture would have been wiped out completely. That is both the Anglo-Saxon legacy of North America as well as the American one that provides a good ground to build an expansionist, but civilized culture that also had a history of succession that could have been easily adapted to a more oligarchic form that would have allowed Caesar's lack of heirs to cause less trouble down the line.
The NCR unintentionally shows that evolutionary Anglo-Saxon world view in their aping of the prewar US, though it ignores the fact that a part of that tradition isn't simply repeating the same thing over again not understanding why, but finding a new take on he old without trying to rewrite the book as seen in the US drawing inspiration from Pre-Conquest England while seeking to create a fundamentally different society of it that was still built upon its fundamentals.
Having two shades of American successor culture fighting one another (and something not comical like the Enclave) is also more organic and plausible than a wannbe Roman Empire popping out up out of the mind of one man and expanding across a sizeable section of CONUS in matter of a few decades.
But that would be too Kwan too keep Kwan, Kwan for many here.
Like Trajan was by Nerva?
When it comes to governance don't look to when things work their best, look to when they work their worst. When Rome's lack of succession laws worked they allowed them to really be flexible, but when they didn't, and they failed more often than they succeeded, you have things like Year of the Five Emperors and the Crisis of the Third Century.
Again, all of this depending on one man, or two if you get a True Believer Courier up against the will of the Legion, a group of people that are effectively being deceived by Caesar himself when it comes down to it as a vector for his utopia all of them would find a betrayal of what they love about their society, which is to murder and enslave everyone civilized.
To go back to the Mongols, that is the exact opposite of Ghengis Khan, who was a tribal leader that believed in the same aims as his Horde and sought to better his people and his family by invading, usurping and preserving all the good things of the more civilized to their own benefit.
Caesar is too high minded, thinking too abstractly and planning things that are too inflexible relying on everything working as he intended, and if they don't, things all fall to pieces and destroy everything he intended, and they can't help but given that he is using the will of those under him as a tool ignoring the fact that he is riding a tiger that has it's own aims.
I can't see the last two pics you put up, but judging by the above they're all shades of Russia, which is a very different culture from North America stuck in a love/hate relationship with their leaders both hating their oppressive/coercive ways while seeking them out as unifiers to leader and direct the people to do greater things because Russians are an indolent, easy going people that like essentially enjoy the small parochial life they've enjoyed for thousands of years.
Anglo-Saxons don't have that outlook at all. At its purist they tolerate enough government to keep things orderly enough to allow them to build their own part of society with their own initiative while obeying it and following its aims as payment for government doing its job. What they hate above all else is anything that gets in the way of that relationship, and you see it repeated through our history from the monarchy and the people banding together to undercut the aristocracy again and again in England going back to Alfred the Great and today's civic revolt against the Washington establishment in the US taking place right now.
Now you can roll your eyes at that like I know you do with anything Kwan, Draco, but keep in mind that the most annoying facets of "Kwan" I've seen you post about come directly from the breakdown in that Anglo-Saxon cultural basis in places like America and Britain.
You may find our culture puzzling and revolting in ways, just as I find the Eastern European one, but it's a respectable one when it's integrity is in tack, just as yours is from my perspective (and be honest, respect, from being a strong brother culture to a worthy enemy is what Russians and Russophiles have always sought from the West and above all the Anglopshere since you rejected Peter the Greats aims of joining it).