Perhaps a fanfic where Beast Boy has to prove himself to a new group of heroes. He goes through a series of trials that really test his limits and his badass side comes out as he overcomes each one, showing his unique combat skills using his shapeshifting.
A really cool plot for a Beast Boy Titans North fanfic would be if there was a mystery in Titans North related to some ancient animal - themed artifacts. Beast Boy, with his connection to animals, gets drawn into the mystery. He could discover that these artifacts have the power to either enhance or disrupt his powers. Along the way, he also has to deal with his own insecurities about being different from the other Titans in North, as his powers are more nature - based compared to some of their high - tech or super - strength powers.
A plot could involve a new villain who targets their relationship. This villain could create illusions or situations that make Raven and Beast Boy question their feelings for each other. But as they fight through these false obstacles, they actually end up realizing that their love is stronger than they thought. For instance, the villain might make Raven think that Beast Boy is only interested in her because of her powers, but Beast Boy then shows his true self and his genuine love for her beyond any powers or abilities.
One idea could be that Beast Boy discovers he has admirers from different dimensions. Each girl from these dimensions has a unique power and personality. For example, a water - controlling mermaid - like girl who is shy but drawn to Beast Boy's kind nature. Another could be a girl from a magical realm who is a powerful sorceress and sees Beast Boy's potential in a different way than others.
One idea could be exploring how his parents' personalities influenced Beast Boy's powers. Maybe his father was a scientist who was working on some genetic experiments that led to Beast Boy's unique ability to transform. Another could be a fanfic where his mother was from a tribe with a special connection to nature, which also played a part in his powers.
One idea could be Beast Boy going back in time to his younger self and having to deal with his past insecurities while still having his current powers and knowledge. Another could be an age - play scenario where he is magically turned into a child and his teammates have to take care of him and protect him from villains who might take advantage of his vulnerable state.
One idea could be exploring the Beast's past more in - depth. Maybe show his life before the curse and how it affected his personality. Another could be a modern - day retelling where Belle is a scientist trying to find a cure for the Beast's curse.
One plot idea could be that Raven discovers she's pregnant and is initially in denial. She tries to hide it from the rest of the Teen Titans, especially Beast Boy, because she's afraid of how he'll react. Another could be a more comical take where Beast Boy accidentally finds out before Raven has a chance to tell him, and he goes into over - protective mode immediately. Maybe he starts reading every pregnancy book he can find and trying to cook special healthy meals for Raven, much to her annoyance at first.
Maybe there's a story where an alien force infects Cyborg's systems and Beast Boy has to turn into various animals to find a cure. Along the way, they have deep conversations about what it means to be different. Cyborg feels like he's more machine than man at times, and Beast Boy, with his animal forms, also has an identity crisis. They help each other come to terms with who they are.
A great plot point could be how he discovers the full extent of his shape - shifting abilities. Maybe he starts off only being able to shift into small animals like mice or squirrels, but through a series of adventures and challenges, he unlocks the ability to transform into larger and more powerful creatures like elephants or dinosaurs. This growth in his powers can be tied to his emotional and mental growth as well.
Slade could be a great main villain. His combat skills and strategic mind would pose a huge challenge for Beast Boy. Beast Boy would have to constantly outwit and outmaneuver Slade, which would really bring out his badass side as he tries to protect his friends and the city from Slade's evil plans.