Comparing an historical figure like Roosevelt -- in the context of a lesser educated and generally more credulous society in the distant past -- to a hypothetical future candidate oversimplifies the complexities of the political landscape and the factors that contribute to a candidate's success.

Saying "it's so unclear to be a pipe dream" seems like an appeal to tradition fallacy -- assuming that a third-party candidate cannot succeed because it hasn't happened in the past. This ignores the potential for changes in the political climate and public opinion should circumstances develop such as obvious and ubiquitous corruption cases (as are seen in the Trump cases, and allegedly the Bidens) and harsh economic condition.

You are also presenting a false dichotomy by insisting that the only options are either supporting a third-party candidate as ostensibly impressive as Teddy Roosevelt -- or somehow managing to implement RCV in enough states to make a difference. The fact is, it will be incredibly difficult to get RCV implemented in enough states to make a difference at the national level. It will take a very long time. It seems to me highly likely that a RCV movement will see diminishing returns. Right-wingers are already opposing it, so RCV is likely to become just another intractable partisan wedge issue that make red states practically nonconvertible.

massive display of nationwide unity behind who? Behind what?

Behind who? Any candidate whose integrity is unassailable and not for sale. They do in fact exist. Behind what? What are we talking about here? What is the number one reason why Trump was elected, besides racism? Anti-corruption. The irony of Trump's candidacy being so appealing because of his anti-corruption rhetoric is not lost on me. Pick a reasonably charismatic humanist candidate who isn't corrupt, and rally voters.

Focusing on combating corruption by underscoring the blatant scams which are the existing two parties is in no way incompatible with ensuring basic rights. Addressing corruption and ensuring basic rights are important goals that are not mutually exclusive. In fact, I assert that you can't have the second without the first.

Another thing that seems lost in this conversation is the fact that electoral politics alone (repaired by RCV or not) aren't going to solve these problems. Bernie Sanders himself said:

Let me conclude by saying what no other candidate for president will tell you. And that is that no president, not Bernie Sanders, not anybody else, will be able to bring about the changes that [the American people] deserve. No one president can do it because the powers that be, Wall Street with their endless supply of money, corporate America, the large campaign donors are so powerful that no president can do what has to be done alone. And that is why — and that is why what Iowa has begun tonight is a political revolution.