One plot idea could be that Arya, in her guise as a servant in King's Landing, catches Tywin's attention not for her identity but for her sharp intellect. Tywin, always on the lookout for useful tools, begins to test Arya in subtle ways. For example, he might ask her opinion on various political matters in a veiled attempt to see if she has any insights that could be of use to him. Another idea is that Arya, while still hating the Lannisters, realizes she can use Tywin to gain access to information that could help her in her long - term revenge plans. She has to balance her hatred and her need for secrecy while Tywin remains oblivious to her true nature.
A possible plot could be a scenario where Arya is captured by Tywin's men. Instead of killing her immediately, Tywin is intrigued by her defiance. He decides to keep her close, thinking he can break her spirit and turn her into a weapon for the Lannisters. Arya, on the other hand, is constantly looking for ways to escape and get her revenge. Their interactions would be filled with tension, as Arya tries to hide her true identity and Tywin tries to mold her into something he can control.
One interesting scenario could be Arya disguising herself as a servant in Tywin's camp. She could overhear his strategic plans and use that information to her advantage later. Maybe she even manages to steal something important from him without him realizing it was her.
Arya and Tywin could also interact in a more unexpected way. Maybe in a situation where they are forced to work together for a short time due to some external threat. During this time, Arya has to constantly remind herself of her ultimate goal of revenge while Tywin is constantly on guard against her, yet also seeing potential in her skills for his own purposes.
One plot idea could be that Daenerys and Arya meet on the road. Arya, being the assassin she is, is initially suspicious of Daenerys. But as they start talking, they realize they both have a common goal of bringing justice to Westeros. Daenerys offers Arya a position in her court, which Arya hesitantly accepts. Together, they plan to take down the corrupt lords and make Westeros a better place.
A plot could involve Arya getting injured on one of her adventures. Gendry, who has a soft spot for her, takes it upon himself to nurse her back to health. During this time, they share stories of their past experiences. Arya tells Gendry about the strange and dangerous things she saw while being a Faceless Man. This closeness could lead to a romantic relationship as they both realize how much they mean to each other.
One plot idea could be Arya, in disguise, getting close to Tywin as a servant in King's Landing. She could overhear his plans and use that knowledge to try and undermine the Lannisters from within. Another could be a scenario where Tywin discovers Arya's true identity but decides to keep her alive for some strategic reason, perhaps to use her as a bargaining chip against the Starks. And a third idea might be a story set in an alternate universe where Arya and Tywin form an unlikely alliance against a common, greater threat, like a White Walker invasion in the south before the events at the Wall.
One interesting Tywin fanfiction could be one that delves into his early years and how he rose to power. It might explore his relationships with his father and the events that shaped his cold and calculating nature.
In some fanfictions, there might be a plot where Jaqen actually has a deeper connection to Arya's family than she initially realizes. Maybe he was secretly tasked with protecting her all along. This could lead to a series of revelations and a change in their relationship dynamics, from mentor - student to something more like comrades in a grander scheme.
A really interesting plot twist might be if Arya discovers that her pregnancy is part of a political plot against her or her family. This would force her to use her skills and wits to protect herself and her unborn child, similar to how she had to survive in the original series. It could also lead to her reuniting with long - lost family members or making new alliances. Well, in this fanfiction, she would have to navigate through a whole new set of challenges with the added responsibility of a pregnancy. She might even have to pretend to be someone else to keep her pregnancy a secret from her enemies. This would be a great way to see her character develop further in a different context.
The relationship could develop into a strange sort of mutual respect. Maybe Arya saves Tywin's life in a situation, and Tywin, in return, offers her protection. They start to understand each other's motives more deeply. Arya realizes that Tywin is not just a heartless monster but a man with his own goals and Tywin sees Arya as a force to be reckoned with rather than just a Stark girl to be eliminated.
One idea could be exploring what would happen if a minor character like Gendry had been secretly trained in magic. He could use his newfound powers to unite the smallfolk against the warring nobles. Another plot could revolve around a female knight from the North who disguises herself as a man to fight in the wars, and along the way, she discovers secrets about the White Walkers that no one else knows. Or perhaps a fanfiction where Daenerys and Sansa form an alliance much earlier and together they reshape the power dynamics of Westeros.