A cool concept could be a crossover where the technology in Gotham and the magic in Star City somehow get mixed up. Batwoman, being more used to high - tech gadgets, and Arrow, who has some experience with magic - related threats, have to combine their skills to set things right. For example, a device that was supposed to enhance Batwoman's suit ends up being enchanted by magic from Star City, and they need to figure out how to fix it and stop the villain who caused the mix - up.
One idea could be a story where characters from different Arrowverse shows team up to fight a new, powerful villain from a different dimension. For example, Oliver Queen from 'Arrow', Barry Allen from 'The Flash', and Kara Danvers from 'Supergirl' could combine their skills and powers to take on this threat.
Maybe the Flash could visit the MCU. He could race against Quicksilver. It would be a really cool showdown of speedsters from different universes. And then the Flash could get involved in an MCU - level threat, like Thanos' invasion but in a different timeline. He could use his speed to try and steal the Infinity Gauntlet from Thanos, creating a whole new plotline for a fanfiction.
Hush could be an interesting choice. He could be spreading false rumors and causing distrust between the heroes and the citizens of both cities. His knowledge of Gotham's underworld and his ability to manipulate people could make him a formidable foe for Batwoman and Arrow. They would need to uncover his true identity and stop him before he completely destroys the relationship between the two cities.
One idea could be a crossover with Supergirl. They could team up to fight a common enemy like Lex Luthor who has some new, devious plan that threatens both Gotham and Metropolis. Another idea is a crossover with the Arrow. The two vigilantes could exchange fighting techniques and learn from each other's experiences in protecting their respective cities.
One idea could be that the Winchesters end up in Star City and team up with the Arrow to fight a demon that is using technology to cause chaos. Maybe the demon has possessed some of the tech - savvy villains in the Arrowverse.
One idea could be a crossover where characters from Arrowverse and Young Justice have to team up to stop a multiverse - threatening villain. For example, Green Arrow and Nightwing leading the combined forces.
One idea could be a crossover of characters from different Arrowverse shows on Earth X. For example, having Barry Allen from 'The Flash' team up with Kara Danvers from 'Supergirl' to fight against the evil regime on Earth X. They could use their super - speed and super - strength respectively to take on the powerful foes there.
Another interesting plot idea is to put Batwoman in alternate universes. In a steampunk - themed Gotham, for instance, she would have different gadgets and face different villains. Or in a world where magic is more prevalent, how would she adapt and fight against magic - using enemies? These kinds of alternate universe stories can bring a fresh perspective to the character of Batwoman.
One idea could be that the Flash from Arrowverse accidentally runs into a different dimension where he meets the Justice League. He then has to team up with them to stop a powerful villain that is threatening both his world and the Justice League's world.
One plot idea could be them teaming up against a new and powerful villain that neither of them can defeat alone. They have to learn to trust and rely on each other's skills in a more in - depth way.