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.
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.
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.
One interesting scenario could be a rewrite of their relationship where Joffrey is secretly influenced by a more benevolent force. This might lead him to treat Sansa with more kindness than in the original series. Maybe he starts to see the value in having an ally in Sansa rather than just using her as a pawn.
One interesting scenario could be Sansa and the Hound meeting again after a long time apart. Sansa has grown stronger and more self - assured, and the Hound is still his gruff self. They might have a conversation where Sansa stands up to him in a new way, showing how much she has changed since they last interacted.
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.
One interesting plotline could be them ruling Winterfell together. Jon as the military leader and Sansa handling the political aspects. It gives a different perspective on how the North could be governed.
There are fanfictions that focus on Sansa Stark's rule in the North. She might face various challenges such as dealing with the harsh winters and the remaining threats from the South. Some fanfics might also delve into her love life. For example, she could have a romantic relationship with a character who was previously just an acquaintance in the original series. It could show how their relationship develops and how it impacts Sansa's growth as a leader.
One interesting plotline could be Sansa and Tyrion forming an unexpected alliance to outwit their enemies in King's Landing. They both have been used as pawns in the political games, and together they could use their wits and knowledge of the court to gain an upper hand.
Some fanfictions focus on Sansa's growth in a different setting. Suppose she travels to Essos and learns new forms of combat and magic there. This would give her new abilities and a chance to come back to Westeros as a more powerful force, ready to claim her rightful place at Winterfell.