Maybe there's a plot where Batman discovers an ancient artifact in the Batcave that has the power of the Beauty and the Beast story. It curses him, and he starts to show more beastly tendencies. Meanwhile, a young woman who is an inventor and a big fan of Batman, tries to create a device to reverse the effects. As she gets closer to Batman to study the curse, they develop feelings for each other and work towards breaking the curse.
One interesting plot might be that Gotham is transformed into a desolate, enchanted place. Batman is the only one who can save it, but he is also affected by the dark magic, becoming more beast - like. A foreign princess who is visiting Gotham for diplomatic reasons gets lost in this new, dark Gotham. She and Batman cross paths, and she starts to understand his pain and his noble cause. They form a bond and try to restore Gotham together.
A plot could be that Batman is cursed by a new villain in Gotham who has magic powers. This curse makes him look more menacing and animal - like. A girl, who is an expert in ancient magic, comes to Gotham to study. She meets Batman and decides to help him break the curse. As they work together, they fall in love.
One interesting plot could be the sons teaming up to solve a mystery that Batman himself has trouble with. They might use their unique skillsets, which are different from Batman's, to approach the case from a new angle.
Well, a cool fanfiction concept could be that Belle discovers a hidden part of the castle that holds the secrets of Beast's past. As she uncovers these secrets, it deepens their relationship even more. Or perhaps a story where Beast gets turned human for a short time and he has to adapt to the human world without Belle by his side at first. He then realizes how much he truly depends on her. Another interesting one would be a fanfiction where Belle's father gets lost in the enchanted forest again, and Beast and Belle have to go on a new adventure to find him.
One way to blend Batman and Beauty and the Beast fanfiction could be to set the story in Gotham. Batman could be the 'Beast' in a sense, isolated in his dark cave - the Batcave. A new character, like a female journalist, could be the 'Beauty' who stumbles upon his world. She might initially be afraid but then start to see the good in him, much like in the original Beauty and the Beast story.
One interesting plot could be Batman and Sherlock teaming up to solve a mystery that involves both Gotham and London. Maybe a criminal organization is operating in both cities and they have to combine their skills. Batman's combat and detective skills in Gotham's dark alleys and Sherlock's deductive reasoning in London's Victorian - like settings would make for an exciting story.
One interesting plot could be Catwoman in the 'Batman Beyond' universe stealing a high - tech item that has the potential to disrupt the new Gotham's power grid. Batman Beyond then has to track her down, leading to a series of high - speed chases across the city's skyline. Another plot might involve Catwoman forming an unlikely alliance with Batman Beyond to take down a new criminal organization that is using advanced technology for illegal activities. And perhaps a plot where Catwoman discovers a secret about Batman Beyond's identity and uses it to her advantage in a heist.
One interesting plot could be that Batman and Lois Lane team up to solve a mystery that involves both Gotham and Metropolis. Maybe a new villain is creating chaos in both cities, and their combined skills are needed to stop it. Batman's detective skills and Lois's journalistic instincts would make for an exciting adventure.
One interesting plot could be Batman teaching Wally about stealth and detective work. Batman's dark and methodical approach would contrast with Wally's more energetic and impulsive nature.
One interesting plot could be Batman teaching Robin advanced combat techniques in a secret, underground training facility. Robin struggles at first but gradually masters the moves.
There could be a plot where the OC is from another dimension. This OC has special powers and lands in Gotham. Batman initially suspects the OC but as time passes, they start to trust each other. Meanwhile, characters like Poison Ivy and Harley Quinn are drawn to the OC's otherworldly charm, leading to the formation of a harem. The group then has to deal with threats that cross dimensions.
One interesting plot could be a ghoul invasion in the Batman Beyond universe. The ghouls start attacking the citizens at night, and Terry McGinnis as Batman Beyond has to figure out where they're coming from and how to stop them. Maybe there's a mad scientist behind it all, creating these ghoul - like creatures using some new technology.