Identity is a big theme too. The male human has to figure out who he is in this new world filled with vampires and werewolves. Is he just an ordinary human, or is there something more to him? This theme often drives the character's development throughout the fanfic.
The exploration of power is also a theme. The male human may gain some unexpected power or have to deal with the power dynamics between the different factions. For example, he could be caught in the middle of the feud between the vampires and werewolves because of his unique position or abilities.
Well, a very common theme is mortality. Since Twilight has vampires and werewolves who are immortal or have long lifespans, fanfics often contrast this with the short and fragile lives of humans. It makes humans more aware of their limited time. Family is also a theme. How human families function in a town where there are vampires and werewolves lurking around. And then there's the theme of fear. Humans are naturally afraid of the unknown and the supernatural, and fanfics often play on this fear, showing how humans either overcome it or are consumed by it.
One common theme is the exploration of the relationship between humans and the Twilight characters. It often involves a human getting involved with a vampire or werewolf from the Twilight world and the difficulties that come with it, like differences in lifespan.
One common theme is the struggle for normalcy. Since the Twilight world has so much supernatural stuff, the human characters often strive to keep their normal lives. For example, in many fanfictions, human characters try to hold on to their regular school and family life while dealing with the knowledge of vampires and werewolves.
One common theme is love. Just like in the original Twilight series, fanfics often explore different types of love between the characters. It could be the intense, all - consuming love like Bella and Edward had.
One common theme is the idea of a human falling in love with a vampire or werewolf, much like in the original Twilight series. It's about the forbidden love and the challenges that come with it.
One common theme is the exploration of human emotions. Since Edward is usually a vampire in the original, when he's human in fanfiction, there's a lot more focus on his basic human feelings like fear, vulnerability, and simple joys. For example, he might experience the fear of getting sick or the joy of a first love without the vampire - related complications.
Love across boundaries is also a prevalent theme. Since both universes have different types of supernatural beings, fanfictions often explore romantic relationships that cross these boundaries. It could be a vampire from Twilight falling in love with a werewolf - like being from Being Human, defying the norms of their respective worlds.
Since I'm not aware of many such fanfics, it's hard to say. But it could potentially explore themes of friendship across species, cooperation in a shared adventure, or perhaps cultural exchange between the two characters.
One common theme is the exploration of Alec's power. Writers often dig into how his unique abilities shape his character and his place in the Twilight world.
One common theme is female empowerment. In these femslash fanfics, female characters often break free from the traditional roles they had in the Twilight series. For example, they might not be just waiting for male characters to make decisions for them but are taking charge of their own lives and relationships.