One idea could be a time - travel plot where Fem Robin and Wally end up in a different era in the Young Justice universe. They have to work together to find a way back while also dealing with the challenges of that time period.
Well, in fanfiction, a fem Wally could bring a whole new dynamic. She might be more in touch with her emotions compared to the original male Wally. Robin, on the other hand, would likely have a different kind of relationship with her. Maybe he'd be more protective or their banter could take on a new, more flirtatious edge.
One possible storyline could be that fem Wally and Robin are paired up for a secret mission. They have to infiltrate an enemy base. Along the way, they start to realize their feelings for each other as they rely on each other's skills to survive.
One idea could be that when Wally returns, he has new superpowers. Maybe he gained the ability to manipulate time during his time away, which he has to learn to control. This could add a whole new dynamic to the team as they deal with the implications of such a powerful ability.
Their relationship could start with friendly banter. They tease each other during team meetings or training sessions. This light - hearted interaction can gradually turn into a deeper friendship as they start to rely on each other more during missions.
A plot could revolve around a mystery in Gotham that seems to be related to Raven's dark magic past. Robin, being the detective he is, teams up with Raven to figure it out. Along the way, they discover that there are forces trying to use Raven's powers for evil in Gotham. They have to not only stop these forces but also deal with their growing feelings for each other, which they initially try to hide.
One idea could be a story where Nightwing has to train Robin in a new and dangerous combat technique. They could face off against a powerful new villain in Young Justice that specifically targets their mentor - protégé relationship.
One idea could be that Robin is on a solo mission in Gotham and crosses paths with Catwoman. She initially tries to mislead him, but he sees through her tricks. They end up teaming up briefly to take down a mutual enemy who is stealing valuable artifacts from both the Batcave and Catwoman's hideouts.
Maybe in the fanfiction, the harem members are all from different backgrounds within the Young Justice universe. They are brought together by their feelings for Robin. Some are heroes, some are civilians with special knowledge. Their relationships develop as they help Robin solve a mystery that threatens the entire Young Justice world. This would involve a lot of character exploration and relationship building.
Another plot could involve Robin being forced to work undercover as an assassin in a criminal organization. He has to balance his loyalty to the Young Justice and his mission to take down the organization from the inside. He might face moral dilemmas as he has to pretend to be a cold - blooded killer.
One idea could be that Robin is on a solo mission and Deathstroke is hired to stop him. Robin has to use his wits and agility to outmaneuver Deathstroke's superior strength and experience. Another could be that Deathstroke, for some reason, decides to train Robin secretly, leading to a complex relationship between the two where Robin is conflicted about learning from an enemy.