Maybe a story where Superboy discovers a connection between his past and an old case that Batman Beyond is currently investigating. They start to dig deeper and find out that an ancient Kryptonian artifact has been hidden in Gotham and it's the key to a much larger conspiracy involving both their worlds. They have to work together, with Superboy using his powers and Batman Beyond his high - tech gadgets to uncover the truth.
Perhaps they could start off as rivals in the fanfiction. Batman from the present is skeptical of Batman Beyond's more high - tech approach. But as the story progresses, they learn from each other and become a great team. For example, Batman could teach Batman Beyond some of his old - school detective skills, while Batman Beyond shows Batman new ways to use technology in combat and surveillance.
One plot idea could be that Batman discovers Baby Superboy and has to protect him from villains who want to use the baby's powers for evil. Maybe Batman has to figure out how to care for a super - powered baby while also keeping him safe.
One idea could be exploring an alternate universe where Terry McGinnis (Batman Beyond) is pulled into the Injustice universe and has to deal with the morally compromised heroes. He might try to find a way to bring back the true sense of justice among them. For example, he could start by trying to reason with Superman, showing him the error of his ways through his own experiences in his own universe.
Another plot could involve a character from the original Cadmus in the Batman Beyond timeline. For example, a revived clone or an old scientist who has new plans. They could be using the advanced technology of the future to bring back old threats or create new ones. Batman Beyond would have to use his unique skills and gadgets to deal with this. He might also team up with some of the new heroes in the future Gotham to take on Cadmus.
A great plot could involve Nightwing training a new generation of heroes in the 'Batman Beyond' universe. He could share his old - school combat techniques with the more tech - reliant heroes, leading to some interesting clashes and growth. For example, he might have a hard time getting used to the new gadgets while the younger heroes struggle with his more hands - on combat style. And together they have to face a villain who is exploiting their differences.
One idea could be exploring a new villain in Neo - Gotham. Maybe a tech - based criminal who can hack into the Bat - suit's systems, creating a whole new set of challenges for Terry McGinnis. Another could be a story where Terry has to team up with an old - school Batman villain who has somehow resurfaced in the future, like the Riddler, but with a new high - tech twist on his riddles.
Maybe the twins are new villains in Gotham. They have unique powers that they use to challenge Batman Beyond. For example, one has the power of illusion and the other has super strength. Their combined efforts make them a tough foe for Batman to face.
One idea could be to explore a future where Batman Beyond has to face an old enemy from the original Batman's time that has been resurrected with new, advanced technology. This would create a clash of old and new styles of combat and detective work.
Well, you could write a fanfiction where the Joker somehow returns in Arkham Beyond, but he has a new, more terrifying form. Batman must figure out how this is possible and stop him before he causes even more mayhem. Or perhaps a story centered around Harley Quinn trying to redeem herself in the Arkham Beyond setting. She could team up with Batman to take down a common enemy, which would create an interesting dynamic between the two characters.
Well, a plot could revolve around Poison Ivy being accidentally awakened from a long slumber in the 'Batman Beyond' era. She finds that the world has changed so much that she's almost an alien in it. However, her powers start to mutate in strange ways due to the new environmental factors. Batman Beyond has to figure out how to stop her while also trying to understand what's causing these changes in her. It could also be that she has a connection to a new bio - tech company in Gotham and is using their resources to spread her plants in a more insidious way.