One possible plotline could be that Batman confesses his love for Wonder Woman during a dangerous mission. They're in a tight spot, and he realizes he might not get another chance. So he blurts it out, adding a whole new layer of tension to their already complex relationship as superheroes.
In some fanfictions, Batman might confess because he sees Wonder Woman getting closer to another hero. Jealousy could be a driving factor. For example, if she's spending a lot of time with Superman on a joint project. Batman, who has been harboring feelings secretly, decides it's time to speak up.
Maybe it takes place in an alternate universe where the world is a bit different. Batman is more open with his emotions. He takes Wonder Woman to a special place, like an ancient, hidden garden. There, he tells her how much she means to him, not just as a teammate but as someone he has romantic feelings for. He might talk about how her strength and beauty have always attracted him, and how he has been trying to hide these feelings for a long time but can't anymore.
One possible plotline could be that Batman sacrifices himself to save Wonder Woman from a powerful enemy. Maybe he takes on a self - destructing device or holds off a horde of villains while she escapes. Another could be that he is poisoned by a new and deadly toxin, and in his final moments, he imparts some crucial knowledge or advice to Wonder Woman.
The confession could also lead to new team - ups. Maybe they start to work together more closely on missions, combining Batman's detective skills with Wonder Woman's combat and diplomatic abilities. This could result in a more efficient way of handling threats in the DC Universe. It could also open up new storylines where they have to face enemies who target their relationship specifically.
A common plotline could be that Batman gets involved with another female character. Maybe he starts to develop feelings for Catwoman due to their shared history of being on the wrong side of the law sometimes. This new relationship on Batman's part could make Wonder Woman feel betrayed and her heart broken.
One popular theme is the love triangle between Superman, Wonder Woman and Batman. Writers often explore the complex relationships that could develop among them. Another theme is them teaming up against a powerful enemy that none of them could defeat alone. This shows their combined strength and the importance of their alliance in the DC universe.
Perhaps a storyline where Wonder Woman discovers a new aspect of her connection to Athena with Batman's help. They could go on a journey to an ancient land that was once under Athena's protection. Along the way, they face various challenges and enemies. This would allow for character development for both of them, as they learn more about each other and themselves in relation to Athena's legacy.
Their relationship is a big draw. In New 52 fanfiction, their relationship can be explored in different ways. It could be a platonic partnership where they respect each other's abilities, or there could be a hint of something more romantic. Writers often play with this ambiguity to create interesting stories. Also, how they deal with the different worlds they come from - Gotham's gritty crime and Themyscira's mythical realm - coming together in the stories is quite fascinating.
The idea of alternate universes is also quite popular. For example, a universe where Catwoman is a hero from the start and partners with Batman and Wonder Woman more closely. Or a world where Wonder Woman has different powers and how that affects her interactions with the other two. Redemption arcs, especially for Catwoman, are also common. Writers explore how she might fully turn to the side of good and what that means for her relationships with Batman and Wonder Woman.
One possible plotline could be that Batman and Wonder Woman are forced to work closely together on a mission that spans multiple dimensions. As they face various challenges, they gradually realize their feelings for each other. For example, Batman, who is usually so stoic, starts to open up to Wonder Woman about his past traumas, and she in turn shares her own insecurities about being an Amazon in a man's world.
In some fanfics, like 'The Amazon, the Bat and the Cat', the plotline involves a magical artifact that can only be retrieved by the combined skills of Batman, Wonder Woman and Catwoman. This forces them to cooperate in a way they haven't before, with Wonder Woman using her strength and magic, Batman his detective skills and Catwoman her agility.