A great plot could be about a female character from 'last kingdom fanfiction' who disguises herself as a man to join the army. She then has to constantly hide her identity while also dealing with the challenges of war and her growing feelings for one of her comrades.
Another interesting plot could be set in a time of peace after the main events of the series. The characters now have to deal with rebuilding their society. There could be political intrigue as different factions vie for power, and old enemies might have to work together. This could show a different side of the characters we know from the series.
A cool plot for 'the last kingdom fanfic' might be to have a character be transported back in time to a crucial moment in the kingdom's history. They would have the knowledge of what's to come but struggle to convince others to believe them. This could lead to all sorts of interesting twists. Or you could write about a character who is secretly training a group of women to be warriors in a society that doesn't really accept that. It would be about breaking gender norms and the challenges they face in a war - torn world.
One idea could be exploring the backstories of the new characters introduced in Kingdom Hearts 3 in more depth. For example, you could write about how they came to be in the different worlds and what their true motives are.
One idea could be exploring the backstories of the minor characters in the 10th kingdom. Maybe a story about the life of a random villager and how the events of the main story affected them.
One idea could be that the Heartless somehow find their way into the Marvel universe and start attacking various locations. The Avengers, being the protectors, team up with Sora and his friends from Kingdom Hearts. They initially have some clashes due to different fighting styles and ways of understanding the world, but eventually learn from each other and combine their powers to defeat the Heartless. For example, Iron Man could use his technology to analyze the Heartless' weaknesses, while Sora uses his Keyblade to directly combat them.
One idea could be that Sora finds himself in a new world where he is surrounded by characters from different Kingdom Hearts realms who all have a strong attraction to him. They compete in a friendly way to go on adventures with him.
Well, a great plot for a Kingdom Hearts 3 Aftermath fanfiction could involve the relationships between the different characters. Like, how Riku and Kairi's friendship might have evolved. Also, since Xehanort was defeated, there could be a power vacuum. Some villains might try to take advantage of it, and the heroes have to stop them before a new, greater evil rises. It could also show the daily lives of the characters in a more peaceful time, with little hints of the past adventures.
One idea could be exploring how the dalmatians' world is connected to the Kingdom Hearts universe in terms of magic. Maybe the dalmatians have a special kind of magic within them that can help Sora in his battles. Another could be a story where the dalmatians are being hunted by Heartless and Sora has to protect them. Also, perhaps there's a secret about the dalmatians' spots that has significance in the Kingdom Hearts lore.
Well, you could write a fanfiction where Hawkeye has to train a new generation of Mohicans. This would involve him teaching them the skills he learned from Chingachgook. It could also include the cultural exchange between the new Mohicans and the settlers in a more positive light. Or perhaps a story where the spirit world of the Mohicans plays a bigger role. The spirits could guide the living characters to make certain decisions that change the course of their lives.
One idea could be exploring what happens after the events of the show. Maybe the crew discovers a new, hidden civilization. Another could be a character - centric fanfiction, like focusing on the backstory of a minor character and how they ended up on the ship. A third idea is a time - travel fanfiction where a character goes back in time to change a crucial event in the ship's history.
There could be many. For example, some fanfictions might focus on alternate endings for certain characters. Maybe a character who died in the original story gets a new lease on life and goes on to achieve great things.