In this fanfiction concept, I would use time travel to ensure that Robb Stark didn't break his vow to the Freys. His decision to marry Talisa instead of a Frey girl led to the Red Wedding massacre. If he had honored his agreement, he would have kept the Freys as allies, and his military campaign might have had a different outcome. Maybe he could have even taken the Iron Throne in the end.
Time travel in a Game of Thrones fanfiction can have a huge impact on the storyline. If a character travels forward in time, they could bring back knowledge of future events and try to prevent disasters. Or if they travel back, they might accidentally change things that were meant to happen. This could lead to different characters rising to power or falling from grace. For example, if a time traveler influenced Tyrion's trial, the outcome could change his entire future and the future of the Lannisters.
If Jon Snow knew his true identity as a Targaryen sooner, he could have made different decisions. He might have been more assertive in his claim to the Iron Throne. Instead of being a reluctant leader, he could have used his true heritage to unite the North and the other kingdoms against the White Walkers more effectively.
There's also 'Through the Veil of Time in Westeros'. This one stands out because it not only has time travel but also delves deep into the magic and mythology of the 'Game of Thrones' world. The protagonist travels through time and discovers secrets about the origin of magic in Westeros that were previously unknown, and their actions in the past start to have a ripple effect on the present and future of the Seven Kingdoms.
I think Tyrion Lannister would be an interesting character to time travel in a fanfiction. He's very intelligent and cunning. Time travel could be his way to outwit his family and those who have wronged him. Arya Stark could also be a likely character. She has the skills of a faceless man. If she could time travel, she could use her skills to change the past, perhaps by assassinating key enemies before they cause harm. And of course, Melisandre. She has some sort of magic related to seeing the future. It's not a stretch to think she could find a way to time travel in a fanfiction and change the course of events in Westeros.
A really cool 'Game of Thrones fix it fanfiction' is the one that changes the ending for Daenerys. Instead of going mad, she manages to find a more peaceful solution for ruling Westeros. She teams up with Jon Snow in a different way, and together they create a more just and prosperous kingdom. This fanfiction gives Daenerys the redemption arc that many fans thought she deserved.
Well, it can give characters better endings. In the original series, some characters' endings were really disappointing. Fanfiction can rewrite those endings to be more satisfying. For example, Jaime Lannister could have a more heroic end rather than the one he got.
One simple way in fanfiction could be through some kind of magic. Maybe there's a powerful red priestess who discovers Ned's body before it's fully decomposed. She uses her magic to resurrect him, much like Thoros of Myr did with Beric Dondarrion. Once back, Ned could play a major role in the political games again, this time with more knowledge and a thirst for revenge against those who wronged him and his family.
One interesting concept could be changing major events in the Game of Thrones universe through time travel. For example, preventing Ned Stark's execution, which would have huge ramifications on the power struggles in Westeros. Another could be bringing back long - dead characters like Rhaegar Targaryen and seeing how their presence would shift the political and social dynamics.
A really creative plot is when a character from the modern world time - travels into 'Game of Thrones'. For example, in some fanfictions, a history buff suddenly finds themselves in the middle of Westeros. They use their knowledge of the series to try and prevent some of the more tragic events. It's a fun take on the time travel concept as they struggle to fit into the world and also make a difference.