Well, obviously the two main characters are Batman from the normal DC universe and Flashpoint Batman. Batman is the well - known Dark Knight, a symbol of justice in Gotham. Flashpoint Batman is from an alternate timeline, with different experiences and a potentially different personality.
Another idea might be that one Batman is from the future and has come back to meet his past self. The future Batman could show the past version some new technologies and tactics, but also warn him about the potential consequences of certain actions. This could lead to self - reflection for the past Batman and a change in his approach to crime - fighting.
Sasuke would likely be aloof and guarded at first. He might see Batman as just another 'vigilante' like some of the shinobi in his world. Batman, on the other hand, would be cautious and try to figure out Sasuke's motives. Eventually, they could start sharing their combat techniques. Sasuke might show Batman how to use chakra in combat, and Batman could teach Sasuke about the importance of having a strong moral code.
Another plot development could be that Flashpoint Batman tries to convince the regular Batman to change his ways. He might see the regular Batman's methods as too soft or ineffective. This could create a lot of internal conflict for the regular Batman as he questions his own beliefs and methods in the face of this alternate - self's criticism.
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.
Robin could be a great addition. He could act as a bridge between Starfire's more light - hearted nature and Batman's seriousness. His acrobatic skills and detective training could complement both of them in a fight. Another good character would be Nightwing. He has a connection to Batman already and his charm could add an interesting element when interacting with Starfire.
Batman comics date back to the 1930s. Over the years, they've become an icon in the comic book world. The longevity of the series is a testament to its enduring appeal and the creativity of the writers and artists involved.