Since we are talking about Miraculous Ladybug crossover with /tg/, Im working on a crossover with Shadowrun. Basically its the events of the show, but in the Shaodwrun world, around the year 2076 or so. The characters are still heroes and Hawkmoth is still there, but the main story is that Harlequin warns them of a conspiracy that its going on,something involving the miraculouses, but since he is too busy saving the world and doing stuff everywhere else, he asks the characters, specifically Marinette, Adrien and Ayla, to discover and stop the conspiracy, but since they really cant do it in their heroes persona, instead, they are forced to run the shadows to do so (like in the videogames, or the TTRPG itself), and so offer them the help of the OC, who is a more veteran (but not that much) runner to teach them about being shadowrunners.
The idea I have is that chapters will be separated into two kinds. Ladybug chapters, where they have to deal more with akumatized villians and stuff, and Shadowrun chapters, where they either train or go on runs.