It could be a character from another important ninja clan, like Hinata perhaps. Since Hinata has always had feelings for Naruto and her clan is also a significant part of the village, Minato might see it as a good match.
Another possibility is Sakura. Although she has feelings for Sasuke in the original, in this fanfiction, the story could be rewritten so that she realizes her true connection with Naruto and they end up getting married at 12. Their dynamic would be quite different from the original, with Naruto having to prove himself in a new way to Sakura.
He could secretly marry Hinata. In the original series, they have a connection, so in fanfiction, it could be a scenario where they elope or have a secret ceremony for some reason, like to avoid political interference in their relationship.
His friends would also be affected. They might be worried about Naruto's well - being. They know him well and might be concerned that his refusal to marry is a sign of some deeper emotional issue. They would want to support him but also might try to persuade him to consider marriage in the future.
Sakura could be a potential partner. Since they are friends from the original series, a forced marriage situation between them would bring a whole new dynamic. There would be a lot of room for exploring their relationship beyond just friendship.
He could marry Mikasa from Attack on Titan. Just think about it. Naruto's positive and determined personality would contrast with Mikasa's more stoic and protective nature. They could meet through some sort of interdimensional accident. Naruto would be fascinated by the Titans and the world outside his own, and Mikasa might be intrigued by Naruto's ninja abilities.
He could marry Hinata. Even though he's banished, Hinata might follow him because of her deep love for him. Their relationship could develop further outside the village, and they could get married and start a family.
Hinata is a very likely candidate. She has always had strong feelings for Naruto and in a multi - marriage scenario, she could be one of the first to be considered. Sakura could also be a possibility. Despite her initial feelings for Sasuke, in fanfiction, the story could be rewritten so that she realizes her true feelings for Naruto and becomes one of his wives.
He could marry Hinata. They have a pre - existing relationship in the original series. Hinata has always had feelings for Naruto, so it would be a natural choice. In the fanfiction, their relationship could progress more quickly, leading to an early marriage.
Maybe he marries an OC (original character). The author of the fanfic could create a whole new character with unique qualities that attract Naruto during his time away from Konoha.