Another idea is that Arya uses her skills in a completely new and unexpected way. Instead of relying on her typical stealth and combat skills, she might use her wits to manipulate the situation. For instance, she could spread false rumors among the captors that would cause chaos and confusion, allowing her to slip in and save Ned.
The Lannisters as a whole could be the antagonists. They were often at odds with the Starks and had their own political ambitions. Cersei, in particular, might be pulling the strings behind Ned's capture, seeing him as a threat to her power and her children's claim to the throne.
One possible plot twist could be that Arya, being a master of disguise, infiltrates Daenerys' court under a false identity. She initially plans to spy on the Dragon Queen but ends up being impressed by Daenerys' leadership and her quest for justice. This could lead to an unexpected alliance between the two strong - willed women.
Maybe there could be a plot twist where Ned discovers that Ashara has a hidden power. This power could be something magical that is feared in the Seven Kingdoms. Ned has to decide whether to protect her from those who would seek to use or destroy her because of this power, and how this affects their relationship.
A plot twist could be that when Arya saves her mom, they find out that there was a prophecy involved all along. The prophecy states that Arya's actions will set off a chain of events that will either save or doom the Seven Kingdoms. Now they have to decide what to do with this newfound knowledge and whether to act on it or try to keep it a secret.
She might use her new role to bring justice in a different way. Maybe she'd secretly punish the corrupt nobles who escaped regular justice. The Stranger is often associated with death and the end, so Arya could be the one to end the reigns of tyrants in the fanfic world.
Another plot twist could be that the situation Tsunade is in is actually a trap set by an enemy to lure Naruto in. So, while Naruto is trying to save Tsunade, he has to also deal with the real mastermind behind the whole thing. This would add an extra layer of complexity to the story.
Maybe Arya gets caught trying to save Ned at the last moment and is taken prisoner. This would be a huge twist as it changes her whole path from being a free - roaming girl to a captive of her enemies.
One possible plot could be Arya Stark rebuilding the Stark legacy all by herself. She might use her skills as a Faceless Man to secretly eliminate threats to Winterfell and the North. For example, she could target those who had a part in the downfall of her family during the chaos of the Game of Thrones. With her unique abilities, she would be able to move in the shadows and slowly but surely regain the power and respect that the Stark name once held.
Perhaps the plot could involve the two coming together to fight a common enemy. The Targaryen might bring her dragons (assuming this is in a universe where dragons exist in this fanfiction) and Ned Stark could bring his military might and the loyalty of the North. Their marriage could be a strategic alliance that was initially arranged for political reasons but then they grow to love each other. They would then have to navigate the power struggles in Westeros, with many houses vying for control.
The plot could center around the cultural clash between the two families. The Lannisters are known for their cunning and wealth, while the Starks are more about honor and loyalty. So, when a Lannister marries Ned Stark, there would be a lot of adjustments. The Lannister in the marriage might try to bring in their lavish lifestyle, which could be resisted by Ned Stark at first. But over time, they could learn from each other. The Lannister could become more honorable, and Ned Stark could understand the importance of some political maneuvering.