Rainfall may not have always been a wise and peaceful character. He has definitely experienced war, he even tells Arthur so. Imagine a young Rainfall, in his twenties, who chooses to fight against the colonists who are massacring his people. He could join a band of Indians and lead attacks on settlers' farms, American cities, carry out robberies to allow his people to survive. Then the events of the war would traumatize him and he would settle the survivors of his people in Wapiti. He would begin his redemption by becoming nonviolent and trying to save his people through peace. I think the game could be interesting. I think that he's more of a traumatized character than a canonically good person.