Maybe Robb has a secret weapon or knowledge that he uses to turn the tables at the Red Wedding. For example, he could have known about a secret passage in the Twins (where the Red Wedding took place) and uses it to get his men out safely. After that, he could journey to Essos to find more support, like seeking the help of Daenerys Targaryen who also has a claim to the Iron Throne and a grudge against the Lannisters.
One possible plotline could be that Robb manages to escape with a small group of his most loyal men. They then go into hiding, perhaps in the North, and start planning their revenge against the Freys and Boltons. Robb might also try to gather more allies, like the remaining Stark bannermen who are still loyal to him.
The story would change in many ways. Robb's mother, Catelyn, might also have survived if he lived. Their combined presence would have a huge impact on the Stark family's standing. Robb could also have a different approach to dealing with the Lannisters. Instead of being on the defensive all the time, he could be more aggressive with his military campaigns, knowing that he has a second chance at life. Also, his relationship with his siblings, especially Sansa and Arya, who are in difficult situations in King's Landing, could be developed in new and interesting ways.
Maybe the plotline focuses on the cultural differences that the OC brings to Sansa's wedding. For example, if the OC is from Dorne, they might introduce new traditions such as a different style of wedding ceremony or unique wedding gifts. This could cause some intrigue and also some conflict as the Northerners are not used to such things. Also, the OC could be a healer who discovers a plot to poison Sansa during the wedding and has to race against time to save her, all while falling in love with her charm and strength.
In a 'Game of Thrones Afterlife' fanfic, the afterlife could be a place where different houses coexist in harmony or chaos. The Starks, Lannisters, and Targaryens could be engaged in a new kind of power struggle. This time, it's not about the Iron Throne but about something more ethereal, like control over the fates of the living. Their old rivalries and alliances might be re - evaluated and new relationships could form as they navigate this strange afterlife realm.
A 'Game of Thrones' future fanfic might explore the consequences of the events in the original series. For instance, if Jon Snow's true identity becomes widely known, how would that reshape the political landscape? Some might see him as the rightful heir and support his claim to the Iron Throne, while others might oppose him out of fear or self - interest. Also, the White Walkers' threat might not be fully over, and there could be a resurgence of the undead in a different form.
One possible plotline could be that they meet in a secret location. Maybe Rhaenys is on a mission and Jon stumbles upon her. They initially distrust each other due to the complex political situation in Westeros. But as they start to talk, they realize they have more in common than they thought. They both have a sense of justice and a desire to see the realm in a better state. This could lead to them forming an alliance and working together to face the various threats in Westeros.
In a fanfic where Robb wins the war, the Stark family's reputation would be greatly enhanced. Robb would be seen as a great leader. He might also start to reform the feudal system in Westeros. For instance, he could give more power to the smallfolk, which would be a revolutionary change. This could lead to a more democratic - like system in the long run. He would also have to deal with the remaining enemies who might be plotting revenge, so he would need to keep a strong military presence.
Well, one possible plot could be that Robb stumbles upon Arya in the chaos of war. He might be leading his troops and suddenly recognize her among a group of refugees or captives. Then he would immediately take her under his protection, ensuring her safety and vowing to take her back home. This would be a moment of great relief and joy for both of them, especially considering all the hardships they've been through.
In a fanfic, Arya could have a more elaborate plan. She might gather evidence of Walder's treachery against House Stark first. Then, she uses her network of allies (either those she made during her travels or some remaining Stark loyalists) to isolate Walder. She could stage a public trial of sorts in the courtyard of his own castle, where she publicly accuses him and then executes him, sending a strong message to all those who wronged the Starks.
One possible plot could be that Robb Stark manages to avoid the Red Wedding trap. Maybe he receives a tip - off from an unexpected source, like a disgruntled Frey servant. With this knowledge, he could turn the tables on his enemies. He might use his military strategy skills to ambush the Freys instead, and this could lead to a major shift in the power dynamics in the North, with Robb emerging as an even stronger leader.
Well, in a fanfic where Robb finds Arya, they could immediately start making plans to take back Winterfell. Arya's skills could be a great asset to Robb's military campaigns. They might also share stories of their experiences during their time apart, which could strengthen their bond.