Well, he could end up being a rival to some of the noble houses in Westeros. Maybe he'd use his Slytherin cunning to try and gain power. He might start off as an outcast, just like he was at Hogwarts, but gradually find a way to insert himself into the political games of the Seven Kingdoms.
One possible storyline is that Draco gets involved in the fight against the White Walkers. His wizarding skills could be a great asset. He might initially be skeptical about the existence of such creatures, but once he realizes the threat they pose, he could use his dueling skills and knowledge of defensive magic to help the people of Westeros. He could also teach some of the locals how to better defend themselves against dark forces, similar to how he was taught at Hogwarts.
He could form an alliance with the maesters. Draco is quite intelligent and has an interest in knowledge. In the GOT world, the maesters hold a lot of secrets and power. He might use their knowledge of magic (albeit different from the magic in the Harry Potter world) to his advantage, perhaps even try to create new spells or potions using the resources available in Westeros.
His Slytherin pride and ambition would make him a natural fit in the cut - throat world of Westeros. He'd likely be drawn to the power struggles and would try to climb the social ladder. Just like in the Harry Potter series, he'd probably look down on those he considers beneath him.
A plotline could involve Draco's family trying to hide his non - pure - blood origin for generations. When Draco finds out, he could start to question his family's values and actions. He might then try to find out who his non - pure - blood ancestors were and what their story was. Maybe he forms an unlikely alliance with some non - pure - blood characters in Hogwarts as he tries to come to terms with his new identity. There could also be a plot where the discovery of his non - pure - blood status changes his relationship with Harry Potter. Instead of being rivals, they could become allies as Draco realizes the unfairness of the blood - based discrimination in the wizarding world.
One possible plot could be that Draco Malfoy is magically sent to Westeros. He gets caught up in the power struggle between the Starks and the Lannisters. Maybe he tries to use his knowledge of magic to gain an advantage, but soon realizes that the politics of Westeros are far more complex than he expected.
Often, Draco is made into a good guy through a time - travel plot in fanfiction. He goes back in time and gets a chance to redo his actions. This time, he makes different choices, like befriending Harry Potter from the start and working against the Dark side. It's a popular way to rewrite his character as a positive one.
One unusual storyline in Severus Snape and Draco Malfoy fanfiction could be a time - travel plot. Imagine Draco accidentally travels back in time and meets a much younger Snape. This could lead to all sorts of interesting interactions as Draco has knowledge of Snape's future and Snape is just a young, bullied student. They might form an unexpected alliance and Draco could try to change Snape's fate for the better.
One possible reason could be for comical effect. Writers might use this as a way to create a humorous and absurd situation, taking a usually serious or snobbish character like Draco and putting him in such a silly situation. Another reason could be for an alternate universe exploration. In some strange alternate version of the Harry Potter world, different rules and situations apply, and this could be one of them.
One possible motive could be the extreme pressure he feels from his family. His father is in Voldemort's inner circle and Draco is constantly under the threat of not living up to his family's expectations. Another could be the isolation he feels at Hogwarts. Despite being part of Slytherin, he may feel alone due to his own moral conflicts.
Another plotline could be that she was cursed as a child and lost her memories. Years later, she starts to regain her memories and realizes she is a Malfoy. Draco then has to help her navigate the wizarding world that she has forgotten while also dealing with his own feelings about having a long lost sister. It could involve adventures in finding a way to break the curse completely.
One possible plot is that Draco Malfoy discovers he has a non - pureblood ancestor through some ancient family records. This shatters his view of his family's pureblood lineage. He then struggles with whether to keep this a secret or reveal it, fearing the reaction from his family and the pureblood society at Hogwarts.
In fanfiction, this could be the result of a multiverse concept. Suppose there are infinite parallel universes. In one of these universes, the rules are different and somehow the Malfoy family and Nico's family are connected. Draco and Nico might initially be in disbelief but then gradually come to accept it. Their relationship could be full of tension at first, given Draco's often haughty attitude and Nico's own guarded personality. But as the story progresses, they could start to rely on each other and form a unique bond that is different from the relationships they have in their original storylines.