Are You Open to the Experience?
Before you proceed, consider whether you enjoy the idea of a challenge like this. I'm saying this not to dissuade you - I played my share of extremely mentally distant characters, and intend to keep playing them. Rather, I want you to check whether you are open to such an experience in the first place, and aren't doing it purely due to peer pressure or other unpleasant factors. Assuming you consider the exercise at least interesting, or hopefully even enjoyable, proceed.
Someone Else's Shoes
Consider Starting Small
It can be hard to jump in all the way into deep water at once. If it looks overwhelming, especially if it's your first attempt at roleplaying a radically different mentality, consider of meeting halfway between the initial concept and your own mentality. Sort the traits by how far they are from yours, and consider toning down the more radical ones.
Also, consider emulating the mentality of characters who match the archetype but are generally more likeable. For example, Scrooge McDuck is a self-made duck from 1947, has both light and dark qualities, tends to act as the party's leader, and is generally perceived as likeable (which is a major factor for retaining popularity for half a century).
Be Ready to Try Again
The first day I played a character whose views on right and wrong differ from mine, it came off rather unconvincing. That's OK. Few people achieve great success on their first tries.
Look for Deeper Differences
In my experience, a lot of radical differences in views are misunderstood. People often see another believe that X (which they disagree with), and conclude that believing X can only be a result of either malice or hypocrisy, and/or only cardboard villains can believe X (often such conclusions are a two-way street!). Meanwhile, if they dig deeper, they'd find out that belief in X is a reasonable conclusion based on the set of deeper ethical axioms and priorities of the believer.
Some examples of such differences are the views on the balance of equality of opportunity and of outcome, of care vs. fairness vs. loyalty vs. respect vs. sanctity, of utilitarianism and deontology, of moral realism vs. moral nihilism etc. Check out those parameters, and see where they likely differ between you and the character. Try to find the likely values for those parameters in the society he comes from.
The Devil's advocate mentality can be useful for portraying characters you disagree with. Using the fundamentals from the point above, try crafting logically sound lines of reasoning for the character - both for getting a better understanding of his likely behaviour, and for him being able to argue for his own morals in dialogues.
(As a Player) Avoid Presentism and Other Cultural Biases
Presentism can be very detrimental to grasping a radically different culture and for remaining impartial. When contemplating your character, try to maintain a state of mind of an anthropologist, not a missionary. This is probably easier said then done, but just keeping this in mind should help at least a bit.
All Archetypes are Idealised (to Some Extent)
At some point you may look at some detail of your character's archetype and think, 'This doesn't work!' and want to backpedal. But that's OK. Archetypes lean towards being idealisations by their nature. The knight in shining armour, the incorruptible revolutionary underdog, they all get to have flaws and blind spots if examined [too] closely.
The question is how close you want them to be examined, and how much you want to accentuate the negative. That usually depends on the style of the story/campaign. For example, the Superman from the 1978 film is more idealised than the one from 2016, but trying to fit one variant into the other film would likely cause a dissonance that worsens the film overall. The same applies to RPG campaigns.
(The Option of) Gradual Character Development
You don't need to keep the character the same for the whole campaign. Consider which arguments and experiences can change his views. If these are deeply-held views, changing them will be neither easy nor simple. But that's part of the fun: seeing the complexities of changes in reasoning; the changing social dynamics with other PCs and NPCs.
A Word on Burning Wheel/Empires
I must admit I'm not well-acquainted with the system, but from what I know, it encourages campaign events that challenge a PC's deeply-held beliefs, and assumes that while the players are friendly and open to each other, the characters may hold deep disagreement. So my impression is that your goals of trying on such a role fall within the area of expectation for this game line.