It's not appropriate at all. The Miraculous Ladybug brand is about positive values, friendship, and heroism. Creating sexual fanfic would not only violate the spirit of the original work but also might expose young fans to inappropriate content, which is unacceptable in the context of a show that has a large following among the youth.
Definitely not. 'Miraculous Ladybug' is about superheroes, friendship, and adventure. The idea of sex doll fanfiction related to it is completely out of line with the positive and innocent themes of the original work. It would also be considered offensive and not in line with the values the show promotes.
The back story of Miraculous Ladybug involves two magical jewels, the Ladybug Miraculous and the Cat Miraculous. These were created long ago and are used to transform into superheroes. Marinette Dupain - Cheng becomes Ladybug, and Adrien Agreste becomes Cat Noir. There's an evil villain, Hawk Moth, who wants the Miraculouses for his own dark purposes. The story also has elements of friendship and young love as Ladybug and Cat Noir work together to protect Paris from Hawk Moth's akumatized villains.
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.
One sad story could be that Ladybug loses her Miraculous. She's in a tough battle against Hawkmoth, and in a moment of distraction, the Miraculous is snatched away. She feels a deep sense of loss and failure as the city is now more vulnerable than ever without her as the full - fledged Ladybug.
One great Miraculous Ladybug love story fanfiction is 'A Miraculous Love'. It focuses on Ladybug and Chat Noir's relationship evolving beyond their superhero duties. The author beautifully describes their hidden feelings and the tender moments they share.