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.
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.
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.
Some fanfictions might have a plotline where the team has to face an old enemy that has been resurrected or empowered by the events of Endgame. This could lead to intense battles and strategic planning. There could also be a story about the relationships between the characters evolving. For instance, romantic relationships might form or existing friendships could be tested as they all deal with the new world order after Endgame.
Perhaps a plotline where the fanfiction delves deeper into the backstories of some of the less - explored characters in the context of the 'Auld Acquaintance' arc. It could show how their past experiences shape their actions and decisions during this particular story arc.
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.
One interesting plotline could be them having to deal with a new and powerful villain that specifically targets their relationship. For example, a villain who tries to turn them against each other by manipulating their past traumas. Another plotline might be them training a new group of young heroes in Young Justice together. It would show their different teaching styles and how they complement each other.