There could be a fanfiction where Ra's al Ghul has a change of heart due to Sara's influence. Sara, with her own complex past, shows Ra's a different way of looking at life. This could involve a lot of emotional exchanges between them, and perhaps a slow - burn romantic development as they get to know each other on a deeper level.
One great fanfiction might be one where Ra's al Ghul and Sara have to team up to save the timeline. In this story, their initial distrust gradually turns into respect as they face various challenges together. Their different fighting styles and moral compasses create interesting conflicts and resolutions.