A third plotline could be the characters forming new relationships in high school. They could meet other students who are also secretly part of the superhero world or just normal friends. These new relationships can change the dynamics within the young justice group and also lead to personal growth for the characters.
Obviously, the main characters from Young Justice like Robin, Aqualad, and Kid Flash would be there. They are the core of the group and their personalities would create a lot of interesting situations in high school.
One possible plotline could be Percy struggling to fit in at high school while also hiding his demigod powers. Maybe he accidentally uses his powers in front of his classmates during a sports event and has to come up with a creative excuse.
A cool plotline might be Starfire's origin story in the context of Young Justice fanfiction. How she ended up on Earth and her journey before joining the team. It could involve her past relationships on her home planet and how they influence her actions on Earth. Also, a plot where she discovers a new power within herself while training with the Young Justice group, which then becomes crucial in a big battle against a supervillain.
Perhaps there's a plotline where a new member joins the team during this 'in - heat' situation. They have to quickly adapt to the intense conditions and the team dynamics. The new member might have a power related to heat, like the ability to manipulate fire, but they first need to learn how to control it properly within the context of the team and the ongoing heat - related challenges.
Another fascinating plotline is when an ancient evil from Ben's world crosses over into the Young Justice universe. This forces both Ben and the Young Justice team to put aside their differences and combine their skills and powers to defeat this new threat. It usually involves a lot of research into both universes' mythologies, and the story can show how the two groups learn from each other and grow together as they face this powerful enemy.
One interesting plotline could be Robin trying to prove himself to Batman in a more complex and dangerous mission within the fanfiction world. Maybe there's a new villain in Gotham that only Robin can stop, but Batman is hesitant to let him take the lead at first.
One interesting plotline could be Robin and Superman teaming up to solve a mystery that involves both Gotham and Metropolis. Maybe a new villain is using technology from Gotham to target Metropolis and only their combined skills can stop it.
A possible plotline is that Wally's immortality is a curse rather than a blessing. He might see all his loved ones die over the years and struggle with loneliness. He could also be hunted by those who want to study or use his immortality for their own gains. In the Young Justice universe, this would make for some exciting and emotional story arcs as he tries to keep his secret and still be a part of the team.
Maybe in the fanfiction, Robin is misplaced in time rather than space. He could end up in the past, having to interact with younger versions of his teammates or even their predecessors, and has to use his wits to not disrupt the timeline while also finding his way back. This would involve a lot of character development as he sees his friends in a new light.
One interesting plotline could be a battle between two underrated Young Justice characters where they finally get to showcase their full powers. For example, a fight between Beast Boy and Terra in a death battle scenario where Terra has more control over her powers than in the original series. This could lead to a very different outcome and a whole new exploration of their relationship and abilities.