One idea could be that Ladybug and Chat Noir face a villain who can manipulate time in the future. This would force them to not only fight in the present but also find a way to prevent the villain from causing chaos in the future. Another plot could involve a new Miraculous holder from the future coming back to help them in their present battles, bringing with them new powers and a different perspective on their fight against evil.
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.
One idea could be a story where the Peacock Miraculous has a unique malfunction that causes it to create unexpected akumas. For example, instead of creating the usual villains, it creates akumas that have the power to spread positive emotions but in a chaotic way that still disrupts Paris. Another idea is a fanfiction where the holder of the Peacock Miraculous has to team up with Ladybug and Chat Noir to fight against an ancient evil that is specifically drawn to the power of the Peacock. This could involve exploring the history of the Miraculous and its connection to this new threat.
One idea could be a crossover where the Miraculous heroes and Ben 10 team up to fight a common enemy. Maybe an alien villain that is immune to the powers of the Miraculous but Ben's alien forms can counter. Another could be a situation where Ladybug's Lucky Charm combines with one of Ben's alien gadgets to create a super - weapon. And a third could be a story where Ben gets akumatized and the Miraculous heroes have to figure out how to save him without using brute force as his alien forms are very powerful.
One idea could be Multimouse getting lost in an alternate dimension where the rules of the Miraculous are different. She has to figure out how to use her powers in new ways to get back home.
One idea could be that the Miraculous Phoenix has the power to heal not only physical wounds but also emotional traumas. The story could follow a character who is deeply scarred by past events and is chosen by the Phoenix Miraculous. As they learn to use its powers, they gradually heal themselves and those around them.
One idea could be Carapace getting a new power upgrade and having to learn to control it while facing a powerful new villain. Maybe he teams up with a new Miraculous holder.
One idea could be that during Halloween, the Miraculous holders have to deal with akumas that are inspired by classic horror movie monsters. For example, an akuma that turns into a vampire - like creature, making people fall under its spell and causing chaos in the city. Another plot could be a Halloween party where the villains try to steal the Miraculous in disguise, adding an element of mystery and danger.
A plot where there is an international Miraculous team-up. Heroes from different countries with their own Miraculous come together to face a global threat. They have different fighting styles and powers, and it's a challenge for them to work together against a common enemy in this showdown.
One idea could be that the fox Miraculous has some unique powers that are not fully explored in the original. For example, it can create illusions not just of objects but also of emotions, which the fox - themed hero uses to calm down akumatized villains.