One idea is that their son would be a bridge between two different worlds. He would grow up with the values of both Batman and Wonder Woman. In the fanfiction, he could face challenges that neither of his parents faced. For instance, he might have to deal with the politics between the Amazons and the humans. His powers and skills would be put to the test as he tries to bring peace and understanding between these two groups. He could also form new alliances, using his unique heritage to his advantage.
Well, in such a fanfiction, the son could inherit amazing powers. Maybe he has Batman's strategic mind and Wonder Woman's super strength. He could use his skills to fight new villains in Gotham or Themyscira.
There could be an ancient evil that is awakened by the birth of their son. This entity could see the son as a threat to its plans for world domination. It might have powers that are beyond what the son initially thinks he can handle, but through his own growth and the help of his parents' friends, he is able to overcome this powerful antagonist.
He could have super strength from Wonder Woman. This would allow him to lift heavy objects and overpower strong foes. Also, he might inherit Batman's martial arts skills, making him a great fighter in close combat.
One possible story could be that Batman and Wonder Woman discover a young orphan with special powers. They decide to take the child under their wing and train the child to be a hero. The child could learn Batman's detective skills and Wonder Woman's combat techniques, creating a unique hero for the DC universe in this fanfiction.
Darkseid is another potential foe. He could be interested in the son's unique heritage, wanting to either corrupt him or use his powers for his own evil purposes. Given Darkseid's power, the son would have to rely on both his Batman - like wits and Wonder Woman - like strength to oppose him.
One interesting storyline could be the son's struggle to balance the very different legacies of his parents. He might have Batman's brooding nature and tactical mind, while also having Wonder Woman's sense of justice and connection to the gods. This internal conflict could lead to some great character development.
She could be devastated. Wonder Woman might go into a period of mourning, isolating herself from others as she grapples with the loss. She was used to having Batman as an ally, and his death would leave a big hole in her life.
In the fanfiction, perhaps Wonder Woman is trapped in some sort of magical or technological prison created by an enemy. Batman, with his detective skills, figures out how to break in and free her. He might have to solve a series of puzzles or overcome various security measures. He then rescues her and they team up to take on the bad guy who imprisoned her.
In this fanfiction, the story could start with Wonder Woman being intrigued by the tales of Batman she hears from other heroes. She decides to visit Gotham to see for herself. Batman, on the other hand, is initially skeptical of this powerful and otherworldly being in his city. However, as they start to interact, they find that they share a common goal of protecting the innocent. They might face a powerful criminal organization that is using advanced technology and magic. Wonder Woman's super strength and combat skills along with Batman's gadgets and strategic mind would make for an exciting story as they battle the bad guys together.
His connection with Gotham City. Batman has a deep and personal connection with Gotham, and the city almost seems to be an extension of him. In fanfiction, Wonder Woman, who is more associated with Themyscira, might envy this strong bond. She may feel that his relationship with Gotham gives him a unique identity that she lacks in relation to any particular place.