Okay but what if Bucky didn’t fall off the train but events still conspired so Steve and Bucky both end up in the modern world???
So Steve manages to just grab Bucky’s hand as he’s hanging off the side of the train. Steve does save him, hauls him back onto the train, and they both huddle in the corner far away from the opening for a minute to catch their breath. (Maybe, because of the adrenaline rush and sitting so close together and clinging to each other for dear life, there’s some intense eye contact that leads to a kiss? Not necessary, but a nice thought).
So after a minute they get up and continue the mission, being much more careful about the shield and deflecting tesseract-fueled shots. Bucky doesn’t pick up the shield again, but he’s always got Steve’s back. Mission is a success, Zola is shipped back to camp and the Commandos all celebrate that night.
Because they now have Zola and Steve is pretty chill because he’s got his best man back and everything is great, blood work and science are done and another version of Steve’s serum is made. It’s not exactly the same, but it’s enough. The first person to test it out is Bucky, of course.
Now Bucky and Steve mow down Hydra and Nazi bases like they’re nothing, always with the Commandos at their backs. They become famous, legendary, and a great morale-booster for other soldiers.
The war is winding down, but Red Skull is still at large. Peggy does her thing and gets all the information needed to track him down in a matter of days. Steve and Bucky are sent out to take him down, lethal force encouraged.
So yeah yeah they fight, Red Skull is banished with the help of the tesseract and the ship is damaged. Peggy is trying to convince them to land on some ice, to tell her their coordinates. They’re just flirting with her, holding hands tightly as the water rushes closer and closer. The ship can’t be controlled, crashing is their only option.
So they crash, do time as popsicles, get discovered, get slowly woken up in separate rooms. (Bucky has some severe damage to his left arm since his serum wasn’t as strong as Steve’s and his body didn’t heal right. He flew forward into the window, striking it on his left side and shattering his bones. It has to be amputated and fitted with a sweet ass prosthetic. Real high end. Thanks to Tony.) Steve doesn’t know Bucky is still alive and Bucky doesn’t know Steve is still alive. They assume the worst, and both react as Steve does in the movie.
But they run into each other in a hallway near some nice big windows and fall over. There’s a pause, confusion, grins, hugs, (again, maybe a kiss? Sure would be nice), and they definitely hold hands.
They’re staring out the window in shock and awe when Fury comes over with his whole “You’ve been asleep for 70 years” bit. They acclimate relatively well since they have each other to rely on. They ground each other, support each other, love each other.
Sam becomes a bud of course, and everything is fabulous because Bucky is just fine and him and Steve are together in the modern world, okay?! (And they’re definitely living together. Nobody questions how close they are, emotionally and mentally and physically. They deserve it and also who cares if two dudes are in love??? Let them live.)
Let some other poor chump be the New Fist of Hydra. Leave Bucky out of it.