Caesar, NCR, Mr. House and Indy/the Courier respectively.
How so? Allow me to explain my theory.
Elijah = Caesar
In Dead Money, we get to know Elijah as the guy pulling the strings behind it all. Elijah came to the Sierra Madre frustrated about his loss at HELIOS One, hoping to "begin again." He hated that the NCR had taken over Helios, something he felt was for the worse. When he came to the Sierra Madre, why did he do it? He wanted to wipe the slate clean and begin again, he wanted to come up with a way to make and break nations. Once he discovered the potential of the Sierra Madre, it was only a matter of breaking in.
The problem? He can't do it alone, he needs help. And his "associates" keep turning on each other in hopes of taking everything the Madre has for themselves.
What is the Sierra Madre but a metaphor for war? "They could've had it all, but they kept turning on each other, letting their greed get the better of them. It....it was insanity." Is this not an aspect of war? If we were to all work together and never declare war on each other, playing as a team, then yes, we COULD have it all. And yet nations turn on each other, hoping to take more for themselves, much like people do on a smaller scale. Hell, from the NCR's perspective, the Battle for Hoover Dam IS a resource war. They prove to be unwilling to share the Dam or the Mojave, if they see a chance to take it all for themselves. Caesar hates the NCR for it's corruption, much like Elijah hates it when his "associates" turn on each other.
So what is Elijah's answer? He installs the dead man's switch to the bomb collars. He attempts to control their greed forcefully. Human nature is still there, but he knows that with the bomb collars rigged to blow together, people will stop turning on each other and work together towards a common goal. Likewise, what does Caesar want? He wants to control humanity. He sees the flaws of humanity and knows the faults of human nature, but he hopes to change this. He hopes to control humanity by building up a nation and controlling it's culture. He knows that if he builds a mighty nation where people are raised to work towards a common goal and not just think of themselves, he can hope to change human nature. The only difference between them is that Caesar is trying to change human nature through generations of indoctrination towards a more noble, selfless way of thinking. Elijah on the other hand accepts human nature for what it is, and simply tries to stop and prevent it's more evil aspects through the use of technology. Both use force (Caesar, through warfare, Elijah through the bomb collars) and both thrive to gain control of the world around them.
Elijah's grand scheme is to master the tech of the Sierra Madre, then "declare war" on the Mojave, wiping out everyone until he's free to build up his own nation the way he likes. Caesar's grand scheme is to keep building onto his army and master the art of war until he conquers literally everyone in the area, then slowly indoctrinate future generations into a culture and nation the way he likes.
And what becomes of them? Sadly, human nature still exists. Elijah may find himself killed by a rebelling "associate" who didn't take kindly to having a bomb collar strapped to his neck, and thus he decided to kill Elijah. Or he may still embrace his greed and steal everything Elijah worked for from right under his nose. Elijah's goal is....too ambitious. He may be strong and determined, but he STILL needs help. The only way for it to work is if he finds someone who shares his philosophies and his goals. Perhaps Elijah could find someone willing to join him by his side in furthering his goals, THEN he could succeed. If he doesn't find a true teammate though, then human nature's need to be free or need for greed is going to destroy him anyways.
Caesar is in a similar situation. He's strong and determined, so much so that he's built up a nation. But Caesar is just one person, and his Legionnaires are following him, not his ideals. Without an heir who properly understands his ideals and wishes to further them, it doesn't look good for the Legion after his death. The people may rebel against the control put upon them by the Legion, wishing for freedom, or even if they don't, people will still be people under his nose. Silus for example is unable to follow through with Caesar's plan, and when his life is on the line, he let's greed overcome him so he can live on.
Joshua Graham = NCR
What is the NCR? The NCR is a nation that wishes to do good. The NCR wishes to give people their freedoms and live happily together, giving everyone a voice and a vote. As a result, the NCR has a multitude of faces, from good to bad. It's a common saying that "the two-headed bear has two heads, wanting to go in two completely different directions, winding up never getting anywhere at all...." The NCR is the nation that, if you listen to their BASIC orders, they actually end up with quite a bad game ending, but if you do your best and try to please everyone, you can actually have the most peaceful ending in the game. The NCR is also a nation that may claim one thing but do the other, seeking excuses to allow for their actions. House himself warns that it's an absolute certainty that, given time, the NCR would simply look for an excuse to kill him and overtake the Strip.
And so is Joshua Graham. Graham is a man with a very wide spectrum of emotions, and a very dramatic moral compass. Much like the NCR represents all different kinds of people with very different opinions, Graham represents all different kinds of emotions with very different kinds of results. Some days Graham wakes up and he's kind and fair to all people, other days he wakes up and he's slaughtering entire tribes, much like the NCR. Perhaps deep down, Graham knows better. He knows God and he knows what doing good means, much like the NCR has proven themselves more than capable of commiting good acts, fully aware of what they are. But sometimes? Sometimes being good is hard. With the NCR, you're asking a nation full of thousands of people to ALL know what's "the right thing to do." Sure enough, many of the people don't or aren't willing to accept the risks that come with being the better man, and thus the NCR compromises itself down to something less good. Graham is much the same. Deep down he knows the truth, but commiting evil? It's just....so easy, so rewarding, so fulfilling. Why take a chance on letting the White Legs go? Why take a chance on letting the Great Khans go? Is it not fair-is-fair to destroy the White Legs? Is it not fair-is-fair to destroy the Brotherhood of Steel?
In the end, what determines what becomes of Joshua Graham? The people around him. The voice of the people can calm him and have him admit the truth: that God is nothing more than an excuse to commit these atrocities. The NCR is the same. It needs the right voice from the right people (the Courier) to refrain from commiting atrocities. Without the right voice from the right people, both give in to their evils, taking care of their problems the easy way rather than the hard way. Graham and the NCR can go anywhere, from commiting genocide to bringing about peace for any and all. The deciding factor will always be the voice of the people.
The Think Tank = Robert House
The Think Tank. A group once dedicated towards progress for the sake of humanity, now isolated in their dome, free to do whatever they please. A group so wrapped up in their own experiments and goals that they've come to believe the Big MT is the only place left on the planet.
House? House is a man who's been isolated from society for centuries, believing in progress as the key to humanity, pragmatic enough to do whatever it takes. He believes Vegas shall be an oasis in the world, a shining beacon of light that promotes progress. He believes his home to be special. House is the type of man that, if he wants something, getting it is just as simple as that. There are no hinderences in his strive for progress. If he believes he's found a hinderence, he disposes of it. House does as he pleases, without much concern for the well-being of others. His philosophy is that if it furthers his goals, then do it. The Think Tank, likewise, will experiment on anything with anything, without any concern for the reprocussions. Whereas House seeks productivity as a whole as his form of progress, the Think Tank seeks knowledge. With House, what becomes of Freeside or outer Vegas is irrelevant, so long as Vegas is still at optimal performance and still progressing forward. With the Think Tank, what becomes of the world is irrelevant, so long as they're still gaining knowledge.
What stands in the way of these two? A form of conscience; idealists. With the Think Tank, Mobius disagrees with their wreckless system of experimentation, dedicating his life to working against them, making sure they never leave the Big MT and hurt the world. With House, it's the Courier (potentially) and many of the people of Vegas (the Followers, the BoS, Freeside). The Courier could decide House will hurt the people and pull the plug, and certain groups like Freeside, the BoS and the Followers simply won't accept the way House does things.
What can become of the Think Tank and House? Well, they could both die. Die because they neglect to care for their fellow man. The Think Tank may die because they give the Courier an ultimatum where he's forced to. They want his brain and his body to further their goals; the Courier has become nothing but a tool to further their goals. And typical of their pragmatic attitude, they don't care that they have to kill him to get these tools. For that reason, the Courier may kill them. Likewise, House may pose a threat to certain groups, believing they need to die to further his goals. The Courier, representing those groups, may kill him when faced with the ultimatum of him or another group. (the Kings, the BoS, the Followers, other communities of Vegas)
Or they could be shown some emotion, compassion and humanity. The Think Tank and House are both the kind of people who simply act on their emotions and desires, while being all-out ambitious in furthering their goals, doing as they please. What if humanity (the Courier) became a part of the Think Tank's desires again? What if humanity took a priority over their experiments? Or hell, what if THEIR lives took priority over their experiments; what if fear (claiming to be Mobius) took control of them? House is the same: as the Courier gains importance, so does his opinion. Perhaps at first, House shoots down his suggestion of sparing a certain group, but as he shows his worth, it suddenly becomes a big deal if the Courier threatens to walk away. Or perhaps the Courier could threaten House; after all, his life is in the Courier's hands.
Ulysses = The Courier (Independent Vegas)
Throughout your travels through the Mojave, what question is probably on your mind?
"What is the right thing to do?"
"What do I believe in/what do I support?"
What is the Independent route? Arguably, of all of the choices, it's the one with the least amount of personal profit. There was a time when we thought Indy meant you're the new ruler, but the developers have since let us know that belief is false. Caesar offers you gold, the NCR offers you bribes and House offers you a life of luxury, but Indy offers you nothing. Indy is a choice that's made solely because you believe in it....or, out of ignorance you believe it'll profit you, and your ignorance costs lives.
The independent Courier is, in a sense, "finding himself." And Ulysses? Ulysses is doing exactly the same. While you're struggling with the conundrum of "war....war never changes. But why?" so is Ulysses. Both of you are searching for something to believe in. The independent Courier has to make decisions purely for himself. These aren't decisions being made for you; no, you have to get to know each nation and decide if you agree with it's existence and philosophies or not. You struggle to determine if Caesar/Elijah's desire for control is justified or not, as does Ulysses. You struggle to determine if the NCR's/Graham's compromising themselves down for more practical results is justified or not, just like Ulysses. You struggle to determine if House/the Think Tank's more selfish outlook on things in a sort of attitude that there IS no solution so you might as well enjoy life and take what you can for yourself is justified or not, and so does Ulysses.
Ulysses eventually decides that he will compromise himself down and take a practical solution in attempt to control the outcome of the Mojave SOMEWHAT, but his interests are purely for the sake of humanity, not selfish ones. Ulysses hates someone who doesn't put thought into their actions, because for an independent path, thought is definitely neccesary or people will die. The conundrum is that Ulysses is still opting to kill people, in a belief that it will save people, similar to how an Indy Courier may opt to destroy the Brotherhood in the Mojave; such is the the struggle of Indy and Ulysses.
And what becomes of Ulysses? What becomes of Indy Vegas?
Simple.
With a little respect for your fellow man and another nation, people live on. Without that respect, people die. Ulysses challenges your beliefs, and if he doesn't feel they're justified, he loses repesct for you. So much so that he declares you and the nation you support "wrong" and opts to kill you. Even if you win the fight, someone has died. If you show him your beliefs are justified, he gains respect for you and the nation you support, opting to let you and that nation live on. He decides to give them a chance, and even fights alongside you in the face of adversity, much like two nations might learn to fight alongside each other. The Courier essentially does this with Independent Vegas. He visits each nation and demands justification. If he receives some, the nation is probably allowed to survive. If he doesn't, he'll likely crush that nation.
Thoughts?
I just found all this interesting to ponder on. There's some lessons in there I think, but I'll leave the conclusions up to you all.