Perhaps the fanfiction focuses on the future relationships of the characters. For example, Marinette and Adrien could be married and facing new challenges as superheroes and a couple. Their relationship might have an impact on how they use their Miraculous powers, and they could be training a new generation of superheroes.
It could involve exciting new Miraculous powers for Ladybug and Chat Noir. Maybe in this 'Peak Future' they have mastered their existing powers to an extreme level, like being able to combine their Lucky Charm and Cataclysm in a more powerful and unique way.
Another theme could be legacy. Since it's about the future, the idea of leaving a positive legacy as superheroes could be explored. They might be mentoring new heroes, passing on their values and knowledge about the Miraculous.
Well, in the context of Miraculous Ladybug fanfiction, a lie for a lie might be about secrets. Marinette has her own secrets as Ladybug, and if someone were to lie about knowing her identity, she might have to lie back to keep things safe. It can create a web of deception that's both exciting and nerve - wracking for the characters and the readers.
It could involve a crossover of the two universes. Black Widow might find herself in Paris and get caught up in the fight against Hawk Moth. She could use her martial arts skills to take on the akumatized villains.
Well, it could be about Ladybug and Chat Noir finally revealing their identities to each other and having to deal with the consequences. Maybe they face a new, more powerful villain that is a threat to all of Paris and they have to use their combined powers in new ways.
Maybe a new character from another country comes to Paris. This character has a Miraculous that has powers related to nature. Their role would be to bring a new element to the team. They could use their powers to heal the damaged parts of Paris that were affected by Hawkmoth's attacks, and also help in battles by using nature - based defenses like thick vines to trap villains.
A new villain could be a former Miraculous holder who turned evil due to some misfortune. Maybe they felt betrayed by the Order of the Miraculous and now seek revenge. Another possibility is an alien entity that is attracted to the power of the Miraculouses and wants to use them to conquer Earth.
In a 'Watching the Future' Miraculous Ladybug fanfiction, Ladybug and Chat Noir might see their future selves facing a super - powerful villain. They could then start training harder in the present to be better prepared.
One idea could be that Hawk Moth finally manages to get hold of both the Ladybug and Cat Miraculouses and the heroes have to find a new way to fight him, perhaps by teaming up with some of the minor characters who develop new powers. Another could be that Ladybug and Cat Noir have to travel to the future to stop an even greater threat that is related to Hawk Moth's actions in their present time.
One plot idea could be that Ladybug and Chat Noir see a future where Paris is in ruins because they failed to stop Hawk Moth. This would give them the motivation to find a new strategy in the present, like seeking out new allies or uncovering a hidden power of their Miraculouses.
In an akumatized Ladybug fanfiction, the akuma might enhance her powers in unexpected ways. For example, her Lucky Charm could become a more powerful and unpredictable object. Her akumatized form might also have a darker and more menacing look, perhaps with a more aggressive fighting style. Writers could explore how the heroes and villains interact with this changed Ladybug.