Pepper Potts can also be a great addition in some of these fanfictions. Even though she's mainly related to Tony, her presence can add a different dynamic. For example, if the fanfiction is about Tony dealing with Howard's legacy, Pepper can be the voice of reason, helping Tony see things more clearly. She can also interact with the memory or apparition of Howard in some creative ways, which makes for a great read.
The portrayal of abuse involving Tony Stark and Howard in fanfiction is quite diverse. Some stories might touch on it to add depth or drama, but not all do. It's really up to the imagination of the fanfic writers.
Iron Man and Howard Stark would likely start with a bit of shock. Howard might be amazed at the technology Tony has created, and Tony would be in awe of seeing his father alive (if it's that kind of scenario). They'd probably exchange some witty remarks, with Howard being a bit more old - fashioned in his speech. Then they'd start discussing technology, with Howard offering some of his classic insights and Tony showing off his modern advancements.
It could be Iron Man, Tony Stark's father is Howard Stark. So Tony would have a very emotional and complex relationship in this meeting. He might be the main character as he gets to know his father in a different way and learn more about his past.
Bucky was indeed responsible for Howard Stark's death in the comic universe. But keep in mind that comic storylines can sometimes be complex and subject to different retellings and revisions over time.
One idea could be a story where Tony discovers a hidden diary of Howard's that reveals secrets about his early inventions and the true motives behind some of his actions. This could lead to Tony having a new perspective on his father and his own work.
Maybe a fanfiction where Tony discovers hidden secrets about Howard's past that change his perspective on their relationship. It could have elements of intrigue and emotional depth.
He might be amazed at the technological advancements. In fanfiction, Howard Stark is a brilliant inventor in his own time. Seeing the future tech like advanced AI and space travel would both astonish and inspire him. He could start thinking of ways to adapt those ideas to his era, or he might feel a bit of envy for not being able to see it all in reality.
There could also be a scenario where the Avengers travel back in time to seek Howard Stark's help. Maybe they need his unique insights on some ancient technology or a threat that has roots in his era. So they go back in time and encounter him.