Another plot could be that Batman is lost in an alternate Gotham City that is far more dangerous and lawless than his own. He has to figure out how to get back home while also dealing with the threats in this new and terrifying place.
Perhaps Batman is poisoned and has to rely on his wits and limited resources to find an antidote before the poison completely incapacitates him. This could involve him facing off against some of his old foes who are trying to take advantage of his weakened state.
One idea could be exploring what if Bruce Wayne's identity as Batman was exposed accidentally by a new high - tech surveillance system in Gotham. Another could be a story where Batman has to take on a new identity temporarily to infiltrate a secret criminal organization that has been studying his every move as Batman.
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 idea could be Batman facing a new, more powerful and elusive villain who has the ability to manipulate time. This would put Batman in a race against time to stop the villain's evil plans.
One idea could be a story where Nightwing has to take over Batman's duties temporarily in Gotham. He faces a new villain who is specifically targeting Batman's absence and Nightwing has to prove himself not just as a replacement, but as a hero in his own right.
One idea could be exploring Batman's internal struggle in the Injustice universe more deeply. Maybe he has a nightmare where he becomes like the tyrannical Superman, and this makes him question his own actions and methods even more.
One idea could be to have Batman and Robin face a villain who has the power to manipulate time. They would have to figure out how to stop the villain from changing history. Another could be that Robin gets kidnapped by a new, never - before - seen criminal and Batman has to use all his detective skills to find him. Maybe a third idea is that a powerful alien lands in Gotham and Batman and Robin have to team up with other heroes to deal with it.
Maybe in the fanfiction, there's an alternate universe where Batman is a father figure to a young sidekick who is still in diapers. The story could revolve around Batman teaching the kid about justice and heroism while also taking care of the diaper - changing duties.
A plot could be where Batman discovers that Artemis has a unique connection to an otherworldly power source that some bad guys are after. They go on a quest to protect this power source. For example, it could be a magical amulet that Artemis has unknowingly been in possession of. Also, they could have a story where they train together. Batman teaches Artemis some of his detective techniques and in return, Artemis shows Batman some new combat moves. This could strengthen their bond and lead to them being a more effective team against threats.
A really cool plot could be that Frozone and Batman meet and decide to have a friendly competition of who can be the most stealthy in a series of challenges across both their cities. However, they soon realize that a new villain is using their distraction to carry out a big heist. So they have to put their differences aside and work together. Another idea is that Violet and Robin become friends and exchange tips on how to be better heroes. Then they use their combined skills to stop a villain who is targeting young heroes in both universes.
One idea could be Batman visiting Themiscyra for some reason, like seeking help from the Amazons in fighting a new and powerful villain in Gotham. Maybe he has to prove himself worthy to get their assistance.