In some fanfictions, a female Obi - Wan might have a different approach to the Force. This could lead to unique interactions with Vader. For example, she could try to redeem him earlier in the story. And perhaps she has a more empathetic connection to the Force which she uses to reach out to Vader's remaining humanity.
One interesting idea could be a female Obi - Wan being a mentor to a younger generation in a different way than the male Obi - Wan. She might use her unique perspective to train Jedi. As for Vader, a fanfiction could explore his relationship with this female Obi - Wan in a more complex way, like they have a grudging respect for each other's skills.
She changes it a great deal. For starters, the gender difference can bring in a new type of relationship. Instead of the more traditional male - male rivalry, there could be an element of attraction or different kind of respect. Also, her way of handling the Force and Jedi teachings might be different, which would affect how Vader reacts to her.
A possible plot could be that female Obi - Wan has a premonition about Anakin's fall to the dark side. In an attempt to prevent it, she tries to get closer to him on an emotional level. As she does this, they develop feelings for each other. However, the closer she gets, the more she realizes that some things are fated to happen. But their love gives her the strength to keep trying to save him from the dark side, and they go through many trials together in their quest to change Anakin's fate.
One possible plot could be that Vader, without his suit, is found by Obi - Wan in a hidden location. Obi - Wan, despite their past, decides to help Vader recover. As they interact, they start to understand each other's perspectives better. Maybe they even form an uneasy alliance against a new common enemy in the galaxy.
Well, here's a plot. Obi - Wan time travels to a parallel universe where the Sith won long ago. He has to find a way to get back to his own universe while also learning from this alternate reality. He might encounter different versions of characters he knows, like a more evil Anakin or a Jedi Order that has completely different values. This could lead to a lot of self - discovery for Obi - Wan as he tries to figure out how to restore balance in his own universe.
One idea could be a story where Obi - Wan and Satine have to team up to solve a mystery on Mandalore that threatens the entire planet. They have to rely on their past connection and trust in each other.
A possible plot could be that female Obi - Wan's pregnancy is the result of some sort of experimental force - related phenomenon. This leads to her being ostracized by some in the Jedi Order who fear the unknown. As she progresses through the pregnancy, she discovers new powers within herself and the baby that could change the fate of the galaxy. She then has to fight to prove that her pregnancy and the baby are not a threat but a potential new hope for the Star Wars universe.
Their relationship might start with suspicion. Obi - Wan would be cautious as he's seen Vader's evil deeds. But as Vader is suitless and perhaps more 'human' in a sense, Obi - Wan could start to see the Anakin he once knew. This could lead to a slow rebuilding of trust.
Yes, there are some 'obi wan married' fanfictions out there. Some might explore an alternate universe where Obi - Wan gets married. However, the quality can vary greatly. You can often find them on fanfiction - specific websites.
One idea could be that young Obi - Wan's Force ghost appears to a young Jedi in training. He imparts some of his early wisdom from his days as a Padawan, like how to better connect with the Force during meditation. Maybe he shows the young Jedi a vision of his own training with Qui - Gon Jinn.
One idea could be that the OC is a young Jedi in training and Obi - Wan becomes their mentor. They go on a mission together to a planet on the Outer Rim where they encounter a new Sith threat. The OC has a unique Force ability that Obi - Wan helps them to develop further, and in the process, they form a deep bond of friendship that could potentially turn into something more.