A character from another dimension or world could end up with the fox Miraculous. They bring their own unique set of skills and knowledge, and their journey in the Miraculous world would be about adapting to this new place while using the fox powers to fight evil.
An existing side character from the Miraculous series could become the main character in a fox - themed fanfiction. For instance, a character who was always in the background but has a hidden connection to the fox Miraculous. They step into the spotlight and become the hero the city needs.
An akumatized villain could be the main character in a different kind of fanfiction. The villain was once a normal person but due to some heartbreak or injustice, they are akumatized into a dragon - like form. The story could then be about their journey of redemption or how Ladybug and Chat Noir try to bring them back to their normal self.
Maybe one of Ladybug's classmates who is also a cheerleader. For example, Alya could be a cheerleader in this fanfiction. She already has a nose for news and is friends with Ladybug, so she could use her cheerleading skills to get closer to the action and help Ladybug in a different way.
It could also be Tikki. As Marinette's kwami, she has a unique perspective. In the 'fifteen again' story, she could be the one guiding Marinette in a different way this time. Tikki could use her knowledge of the past and future to help Marinette make better choices, and through Tikki's eyes, we could see a different side of the story, such as how she views Marinette's growth and the changes in the Miraculous world over time.
Obviously, Ladybug could be the main character. Since it's about cleaning the house, she could be shown in a more domestic side of her life, which is not often explored in the original series.
Ladybug could be the main character. Since she is the main protagonist in the original series, it would make sense for her to be in the center of this fanfiction. She could be the one to witness the car accident, or be directly involved in it somehow, like trying to stop it from happening with her powers.
A young orphan could be a great dog miraculous holder. They have been on their own for a long time and have developed a strong sense of survival. When they get the dog miraculous, they use it not just to fight villains but also to find a family. Their connection with the dog miraculous makes them feel less alone as they have a new 'pack' in the form of the heroes they work with.
A shy artist could be an interesting character. They could use the Peacock Miraculous' power to create beautiful yet powerful constructs. Since they're shy, they might initially be afraid to use it in public, but as they gain confidence, they become a force to be reckoned with. Their artistic side could also influence the way the akumas or amoks they create look, adding a unique aesthetic to the story.
Based on the title, it seems the main character could be the 'queen of mean'.
A new character could be introduced as the main villain. Maybe a corrupt police officer who turns to the dark side. He could use his knowledge of the law and the city's security systems to commit crimes and frame the Miraculous heroes. He would be a formidable opponent as he has insider knowledge.
It could still be Hawk Moth. Since Nathalie has been working with him, getting a Miraculous might make her a threat to his plans, so he could turn against her and become the main antagonist.