Well, Lord Eddard Stark could interact with Gared. Given that Eddard is a nobleman of the North, he might cross paths with Gared, perhaps when Gared was still in the North before joining the Night's Watch. They could have conversations about the state of the North, the rumors of strange things in the far North, which could be an interesting dynamic as Eddard is a man of honor and Gared is just an ordinary man with his own fears and hopes.
Samwell Tarly could also be a character to interact with Gared. Sam is a bit of an outcast in the Night's Watch like Gared might have been. They could bond over their feelings of being different from the other members. Gared could have given Sam some advice on how to survive in the harsh environment of the Wall, and Sam could have shared his knowledge from his studies with Gared.
One idea could be exploring Gared's backstory before he was in the Night's Watch. Maybe he had a family or a love interest in his village that he left behind.
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.
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.
If he met Jon Snow, Loki might be intrigued by his half - wild, half - noble nature. He could either try to use Jon for his own purposes or see him as an ally against the greater threats in Westeros.
Daenerys would be a great main character. She could be a strong - willed CEO of a start - up aiming to disrupt the traditional corporate world, just as she aimed to change the power dynamics in Westeros. Jon Snow could also be a main character, perhaps as a journalist uncovering the dark secrets of the powerful families, similar to his discovery of the White Walkers' threat in the show.
Tyrion Lannister. He is known for his wit and political acumen. Meeting Kratos, a powerful and straightforward warrior, would create an interesting dynamic. Tyrion might try to use Kratos for his own political games or just be fascinated by his stories of battles from another world.
Be cautious. The characters in Game of Thrones can be very unpredictable. Don't trust anyone right away. If you meet a character like Tyrion Lannister, for example, you can start by being respectful and showing intelligence. Avoid making quick judgments. Listen more than you talk at first. If you come across a more hostile character, like Ramsay Bolton, it's best to be submissive until you can find a way to escape or defend yourself.
A samurai - like character from Zipang could be a main character. They would be skilled in combat and bound by a strict code of honor. They could enter the fray in Westeros and become involved in the power struggles, perhaps even challenging the likes of Jaime Lannister in a duel of honor.