I want an AU in which the Winter Soldier doesn’t remember anything (apart from a vague sense of familiarity sometimes) and he deliberately impersonates Bucky.
He choses to do that because with his handlers gone he has nowhere to go, and he remembers Steve’s adamant refusal to hurt him, and this unbearable anomaly is the first thing that shocked him in seventy years, the first thing that actually makes him think.
He gathers information from the Smithsonian, textbooks, archives, the internet, and then lets Steve find him. He admits that his memories were wiped, but his perceptive, serum-enhanced brain is quick at picking up details from Steve’s remarks, to tease out the right answer from the question itself. The first time Steve asks him something he really can’t answers he is terrified to say ‘i don’t know’ and astonished that Steven doesn’t punish him for it, just smiles a little sadly. It takes him weeks to realize that he cannot get caught, he cannot make mistakes because Steve will accept whatever he says and forgive him whenever he is weak and he doesn’t get it, he doesn’t get it but he wants it more than he can say.
He feels more and more guilty about the lie he built, and if it was only for his own good, he would already have come clean. But Steve takes care of him, gives him nice-tasting food and a warm bed to sleep in and a shower where he can rinse seventy years off blood off his skin and a steady hand on his shoulder, and the least he can do for Steve is to give him his friend back. He has a new mission now and that is pleasing Steve - he watches Steve for nostalgic smiles and cold disappointment, and he trains himself like people train dogs, teaching himself broad smiles and coarse language just so Steve can believe he has his friend back.