Well, in some fanfictions, a plot twist might be that there's a third party who already knew their identities all along and has been manipulating events. This third party could be using their knowledge to either bring them closer or drive them apart for their own motives. Also, there could be a plot twist where the big reveal is actually a false one, set up by Hawk Moth to deceive them and gain an advantage in his fight against the heroes.
In some fanfictions, one interesting plot development could be that Ladybug and Chat Noir accidentally reveal their identities during a battle. For example, their Miraculous might get damaged and they transform back in front of each other.
One interesting Miraculous Ladybug Reveal Fanfiction could be 'The Unveiling of Hearts'. In this fanfic, Ladybug and Chat Noir are forced to reveal their identities during a battle against a powerful akuma. The story then delves into how they deal with this newfound knowledge of each other and how it affects their relationship both as superheroes and as the people behind the masks. Another great one is 'Reveal in the Rain' where the reveal happens in a more emotional and unexpected setting, adding a lot of drama to the story.
Another plot twist could be that the thief has a connection to the Miraculous themselves. Perhaps they are stealing Miraculous - related items in order to create a new, more powerful Miraculous. This would put them in direct conflict with Ladybug and Chat Noir, who are sworn to protect the Miraculous.
One interesting plot twist could be that instead of Hawk Moth being the main villain, it's someone from the Swan Lake story who has been corrupted by dark magic. For example, Rothbart could be working with Hawk Moth to create more chaos. Another twist might be that Ladybug and Chat Noir get trapped in the world of Swan Lake and have to find a way to break the curse there in order to return to Paris and continue fighting akumas.
One interesting plot twist could be that Ladybug, while in a fight, is magically transported to the Mulan universe. There, she has to learn Mulan's way of fighting to get back home. Maybe she teams up with Mulan herself against a common enemy like an akumatized Shan Yu.
One plot twist could be that Hawk Moth teams up with Jafar. They both have their own evil plans, and together they become a more powerful force. Ladybug and Cat Noir then have to rely on Aladdin and Jasmine's knowledge of Agrabah to find a way to defeat them. Another twist could be that the Miraculous jewels are actually ancient artifacts from Agrabah that were lost long ago, and Aladdin accidentally stumbles upon one, which draws Ladybug and Cat Noir to his world.
An interesting twist could be that the hypnosis isn't just a simple mind - control. Instead, it's a form of time - travel hypnosis. The characters are hypnotized and sent back in time to when Hawk Moth first got his powers. They then have to figure out a way to stop him from getting the powers in the first place, all while dealing with the disorientation of being in a different time period and the limitations of their Miraculous in the past.
One interesting plotline could be how Ladybug and Chat Noir finally reveal their identities to each other in a very unexpected and emotional moment. Maybe it happens during a battle where they are forced to trust each other completely.
There's also 'Revealed Hearts'. In this fanfiction, the Adrienette reveal is set during a big battle. It adds a lot of drama as they have to deal with their feelings while also fighting off the villain. It's really exciting to read.
There's a fanfic called 'Identity Exposed'. This one takes a different approach. Instead of a grand moment of reveal during a fight, it's a more accidental discovery that sets off a series of events, exploring their emotions and reactions in a unique way.