One common theme is the exploration of gender roles. Since Bruce Wayne is typically male, a female version has to navigate a male - dominated world like Gotham's crime - fighting scene. Another theme is the reimagining of relationships. For instance, how she relates to Robin or other members of the Bat - family might be different.
A prevalent theme is also empowerment. The female Bruce Wayne often has to prove herself in a world that might not expect a woman to be a powerful vigilante. She might face challenges that the male Bruce Wayne didn't, like being underestimated, which she then overcomes in creative ways. And there's also the theme of identity. She has to come to terms with being a female in a role that was originally male - defined in the Batman universe.
Another theme is the passing on of the mantle. Dick is seen as the one who will carry on Bruce's legacy in some way, and fanfics play with this idea, showing the trust and responsibility involved in that transfer of the mantle.
One common theme is vulnerability. Bruce Wayne, despite being Batman, is shown as a human who can be hurt, both physically and emotionally. Another theme is isolation. When he's hurt, he often tries to deal with it alone, which adds to his pain.
One common theme is the exploration of gender roles. How a female Bruce Wayne would break or conform to the traditional male - dominated role of Batman. Another is relationships. Since she's female, her interactions with male and female characters like Alfred, Dick Grayson, and Catwoman can be very different. Also, there's often the theme of how Gotham would react to a female Dark Knight.
One common theme is the battle of ideologies. Bruce Wayne stands for a world of rules and order, while the Joker wants to disrupt it all. Another theme could be redemption, where either character might be on a path to change. Also, the theme of obsession is often present, as the Joker is obsessed with Batman and vice versa.
One common theme is the crossover aspect. Writers often explore how Bruce Wayne would fit into the Smallville universe, like his interactions with Clark Kent and other Smallville characters. Another theme could be the idea of Bruce and Clark teaming up to face a common threat that neither could handle alone.
One common theme is the struggle between love and duty. Bruce has his duties as Batman, and this often clashes with his relationship with Rachel. Another theme is the idea of redemption. Rachel can sometimes be seen as a symbol of normalcy and goodness that Bruce is drawn to, and his relationship with her is a way for him to find redemption from his dark and violent life as Batman.
One common theme could be the daughter's struggle with living in the shadow of her father's legacy. She might be trying to prove herself as a hero in her own right. Another theme could be family relationships. For example, how she interacts with Bruce Wayne as a father, dealing with his overprotectiveness or his high expectations. Also, the theme of identity might be present. Is she a vigilante like her father? Or does she choose a different path to make an impact in Gotham?
There's also the theme of secrecy. Bruce has to keep his identity as Batman a secret, and this creates a lot of tension in the relationship. The reader may suspect something or eventually find out. A lot of fanfics play around with this idea. Also, redemption is sometimes a theme. The reader might be a character who helps Bruce find more balance in his life, between his playboy persona and his role as a vigilante.
A recurring theme is the struggle between their different ideologies. Jason might have a more extreme approach compared to Bruce's more traditional one. This creates conflict and tension in the stories. Fanfics often explore how they can either find a middle ground or accept their differences while still maintaining their relationship.
Common themes in Bruce Wayne x Barbara Gordon fanfics often include the power dynamics within their relationship. Bruce, being a more experienced vigilante as Batman, may initially have a more dominant role. However, Barbara, with her intelligence and skills as Batgirl/Oracle, can challenge that. There's also the theme of family. Bruce's family legacy in Gotham and Barbara's relationship with her father can impact how they view their own relationship. Additionally, the theme of sacrifice is present. They may have to sacrifice aspects of their relationship for the greater good of Gotham.