One character that would be interesting to include is Isaiah Bradley. His story is so rich and tragic, and his connection to the super - soldier program could bring a whole new layer of depth to the fanfic. Additionally, Agent 13 could be included. She could be involved in some sort of political intrigue that Falcon and Winter Soldier have to navigate through. And Redwing! Sam's trusty drone could have its own sub - plot, like getting hacked and Sam having to rescue it.
One idea could be exploring Sam's journey in more depth as he adjusts to being Captain America. Maybe he has to face some old foes who don't believe he's worthy of the shield. Another could be a team - up mission between Falcon and Winter Soldier that goes awry, leading them to rely on their friendship to get out of a tough situation. Or perhaps a story where they discover a new threat to the world that is related to their pasts.
The Winter Soldier is none other than Bucky Barnes. His transformation into this role was a result of manipulation and experimentation. Despite his past actions, he later strives for redemption and works to atone for his deeds.