There could be a fanfiction where Bumblebee is injured during a battle and has to rely on his human friends to repair him. But in the process, they accidentally upgrade his systems in a way that gives him new and unexpected abilities. This storyline would explore how he adjusts to these new powers while still remaining true to his character.
A great fanfiction plot might be Bumblebee forming a special bond with a human child who has the ability to communicate with Cybertronians telepathically. They go on adventures together, solving mysteries that are related to ancient Cybertronian technology hidden on Earth. This would combine elements of friendship, mystery, and adventure.
One interesting storyline could be Bumblebee getting lost on an alien planet and having to team up with local creatures to find his way back to the Autobots. It could involve lots of action as he defends himself and his new friends from hostile forces.
One possible storyline could be that Bumblebee was exposed to a strange energy source that caused an unexpected biological change, leading to pregnancy. He then has to deal with the reactions of his fellow Autobots, some of whom are confused and others who are supportive. Another storyline could be that an enemy has somehow engineered Bumblebee's pregnancy as part of a devious plan to either weaken the Autobots or create a new type of weapon using the new life form.
One possible storyline could be that Bumblebee discovers a new power source but it's in a dangerous area. Optimus Prime has to decide whether to risk the team to help Bumblebee retrieve it. Another could be a story where Bumblebee gets captured by the Decepticons and Optimus Prime leads a rescue mission.
One possible storyline could be that Starscream and Bumblebee are forced to team up during a crisis on Cybertron. Maybe there's a new threat that neither of them can handle alone, so they have to put aside their differences. For example, a powerful alien force arrives and starts attacking the Autobots and Decepticons alike. Starscream, being the opportunist he is, realizes that only by working with Bumblebee can he survive and perhaps gain some advantage later. Bumblebee, on the other hand, is hesitant at first but then sees the bigger picture.
A plot could involve Bumblebee getting damaged and losing his memory. The RWBY characters find him and try to repair him while also helping him regain his memories. As they do this, they learn about the Transformers universe and Bumblebee starts to adapt to the RWBY world, eventually using his unique abilities to help them in a big battle against a powerful Grimm horde and a new villain that has emerged.
Perhaps a fanfiction where Bumblebee gets severely damaged in a battle. Optimus Prime then has to take on the role of not just a leader but also a mentor to help Bumblebee recover both physically and mentally, and in the process, they form an even deeper bond.
A plotline could be Baby Bumblebee getting lost in an alien world. He has to use his wits and the limited skills he has learned from the Autobots to survive. Maybe he teams up with some strange alien creatures who at first seem hostile but end up being helpful.
She could be a spy within the Decepticon ranks. Pretending to be on their side while secretly feeding information back to the Autobots. Her small size and ability to transform into a less - conspicuous vehicle would make her perfect for this role.
Maybe a fanfiction where Dark Energon is being used to power a new super - weapon, and Bumblebee has to infiltrate the Decepticon base to stop it. Along the way, he discovers some secrets about the origin of Dark Energon and its connection to the Transformers' past. This would be an exciting plot full of mystery and adventure.
One plot idea could be that Bumblebee and Arcee have to team up to protect a powerful artifact from the Decepticons. They start off not getting along well due to their different fighting styles, but as they face challenges together, they learn to respect each other and become a great team.
There could be a fanfiction where Bumblebee loses his memory. Arcee takes it upon herself to help him regain it. She takes him to all the places they've been together, shares their memories, and tries to jog his memory. As she does this, she also realizes how much Bumblebee means to her and how important their relationship is. This is a story about friendship, loyalty, and the power of memories.