Often, the Boltons are main antagonists. Ramsay Bolton in particular is a cruel and sadistic character who has caused great harm to both Theon and Sansa. His actions are a major source of conflict in many fanfictions.
It could also be Littlefinger's followers or remnants of his schemes. Since Littlefinger had his own plans involving Sansa, his influence might still linger in fanfiction, and those who were loyal to him could oppose Sansa and Theon's attempts to bring stability to the North.
Another scenario could be a more romantic one. Theon, having redeemed himself, realizes his true feelings for Sansa. They might have a moment where they share their past traumas and find solace in each other, slowly building a relationship based on mutual understanding and respect.
One interesting storyline could be Sansa and Theon teaming up to take revenge on their common enemies. They've both been through so much in the original series, and in fanfiction, they might use their combined knowledge and skills to outwit those who wronged them.
Yes, there are some out there. Some fanfictions might explore the idea of Sansa and Theon having a family in an alternate universe. They could focus on how they raise their baby, the challenges they face in a world full of political intrigue and danger. For example, how they protect their child from their enemies and how they pass on their values to the next generation.
Theon Greyjoy can also be an interesting character to pair with Sansa. Their complex relationship can be developed further in fanfiction. Maybe Theon is trying to make amends for his past actions towards Sansa and they end up forming an unexpected alliance to face common enemies.
If Sansa was pregnant in this fanfiction, it could potentially be a catalyst for a new alliance. Jaime, despite his past actions, has certain skills and influence. This could be used to protect Sansa and the unborn child. However, they would face many enemies. The Lannisters might not accept Sansa easily, and the Northmen may be skeptical of Jaime's intentions. Sansa, on the other hand, would have to use her wits to navigate through this difficult situation, perhaps trying to use the pregnancy to her advantage in the power games of Westeros.
One interesting fanfiction could be where Sansa uses her new - found wisdom and political acumen in a situation that has a 'lemon - like' twist, perhaps in a negotiation with a difficult lord where she offers something unexpected, like a rare lemon - scented perfume from the south in exchange for loyalty. However, this is just a speculation as there are countless fan - created stories out there.
One great fanfiction is 'The Sisters' Reunion'. It beautifully explores Arya and Sansa's relationship after their long separation. It shows how they learn to trust and rely on each other again, with vivid descriptions of the Westerosi setting.
There's also 'Sansa and Arya's New Adventures'. In this fanfiction, they embark on a journey across the Seven Kingdoms to discover secrets about their family. Along the way, they encounter old enemies and make new allies. It's full of action and the exploration of their sisterly bond.