The children of the original characters would be likely main characters. For example, Jon Snow's (if he has any) descendants. They could inherit his sense of honor and face new challenges in the post - war Westeros.
In a 'Game of Thrones Epilogue Fanfiction', it could be about the adventures of the next generation. The children of the main characters might discover new threats or mysteries. For instance, they could find hidden secrets about the White Walkers that were not fully explored in the original series, leading to a new quest.
One main character could be a genetically - enhanced human who has special abilities, like Arya Stark's skills in the original. She could be on a mission to avenge her family who were killed by a powerful space - faring clan. There could also be a powerful warlord from a distant star system, a bit like Ramsay Bolton, feared for his cruelty and thirst for power. The interactions between these diverse characters would drive the story forward in this space - based Game of Thrones fanfiction.
Arya Stark could be a main character. She could use her skills as a Faceless Man to infiltrate the enemy's camp before a big battle and gather intelligence. Her ability to change her appearance would give her an edge in spying and sabotage operations during the battle.
It could be Arya Stark as the bodyguard. Given her skills in combat and disguise, she would make a great protector. She could be protecting someone like Bran Stark as he continues to develop his powers and is a target because of his abilities.
You could have a main character who is a commoner. Maybe a peasant girl who witnesses the fall of a great house and has to navigate the chaos that follows. She could get involved with the various factions vying for power, and through her eyes, we see the events of the prequel unfold. This would give a different perspective compared to the noble - centered stories we often see in the 'Game of Thrones' universe.
Gendry could also play a major role. As a skilled blacksmith and a bastard like Jon, he has the strength and the will to fight for change. He could use his skills to arm the revolutionaries and his knowledge of the common people's plight to inspire them to rise up against the unjust noble rule.
Jon Snow would also make a great main character. He could be on a mission to unite the different houses' spaceships against a common threat, like an alien race or a powerful space - faring pirate group. His leadership skills and sense of justice would be put to the test in this new setting.
The children of Sansa Stark and Tyrion Lannister would be interesting main characters. They would have a unique heritage, being part Stark and part Lannister. Their story could be about bridging the gap between the North and the South, facing the challenges of being accepted in both regions. They might have to deal with the political unrest that still lingers after the events of the original series, while also trying to create a better future for themselves and Westeros.
Skitter from 'Worm' could be a main character. She has the ability to control bugs and her strategic mind would make her a force to be reckoned with in Westeros. Maybe she could start as a low - born character and rise through the ranks using her powers and wits, much like some of the more interesting characters in Game of Thrones.
Jon Snow could be a young journalist trying to uncover the truth about the corrupt power dynamics in the city. He's an idealist, much like in the original, and he's not afraid to take on the powerful families who control the media and politics.