A cool fanfiction idea would be a crossover within the Transformers universe. Have some characters from Transformers Prime interact with the well - known Beast Wars characters in a joint mission to stop a greater threat that endangers both their timelines.
You could write a story about a young Autobot or Decepticon who gets stranded in the Beast Wars era and has to learn how to survive among the Maximal and Predacon factions. They might have to adapt to the different rules and cultures while also trying to find a way back to their own time.
One idea could be a crossover where the characters from Transformers Prime end up in the Beast Wars universe. They could form alliances with the Beast Wars characters to fight a common enemy like the Predacons. Another idea is to explore the origin stories of some of the Beast Wars characters within the context of the Transformers Prime lore. Maybe there's a hidden connection between a Prime character and a Beast Wars character that could be uncovered.
One idea could be that the Autobots and Maximals team up against a new common enemy that has the ability to corrupt both mechanical and organic forms. They would have to combine their different skills and technologies to overcome this threat.
One great 'Transformers Prime Beast Wars' fanfiction story is 'The Hidden Legacy'. It delves into a previously uncharted aspect of the Beast Wars era within the Transformers Prime universe. The characters are well - developed, staying true to their original personalities while also evolving in new and interesting ways. Another good one is 'Alliance of the Primes'. It has an exciting plot that involves a coalition between different factions of Transformers, which is a fresh take on the typical Beast Wars storylines. And 'Beastly Redemption' is also worth checking out. It focuses on a character's journey towards redemption, which adds a lot of depth to the story.
Perhaps Vergil is from a parallel dimension where the Devil May Cry world and the Transformers Beast Wars world are already intertwined. He comes to the Beast Wars universe to seek a powerful artifact that could help him in his own dimension's battles. Along the way, he forms unexpected alliances with both Autobots and Maximals, and his presence changes the course of the Beast Wars as the different factions either see him as a threat or an opportunity.
One idea could be exploring a hidden planet during the Dark Voyage. The Maximals and Predacons could discover a new energy source there that changes the power dynamics. Maybe there are ancient Transformers on this planet with unique abilities.
One idea could be a human character who discovers a hidden power within themselves that can interact with the Cybertronian technology in unique ways. For example, they might be able to heal damaged Transformers using a special energy they possess.
One idea could be exploring Predaking's origin in more depth. Maybe he has memories from before his creation that he slowly uncovers. Another could be a story where Predaking tries to form an alliance with the Autobots against a common enemy, like a new and powerful Decepticon threat.
One idea could be a crossover where the Autobots from Transformers Prime end up in the world of RWBY. They could team up with the RWBY characters to fight a common enemy, like a new type of Grimm that has some technological abilities similar to the Decepticons. The Autobots' advanced weaponry and technology would be a great addition to the RWBY universe's combat.
One idea could be a story where Optimus Prime has to team up with an unlikely ally from another planet. Maybe a small, scrappy alien that has some unique abilities that can help in the fight against the Decepticons. This would add an interesting dynamic as Optimus has to learn to work with a very different being.
A plot idea could be that Optimus Prime time - travels. He goes back to the beginning of the war between the Autobots and the Decepticons and tries to prevent it from starting. Along the way, he meets younger versions of his friends and enemies and has to deal with the consequences of changing the past. Or perhaps, Optimus is trapped in a dimension where the laws of physics are different. He has to adapt quickly and find a way back to his own world while also facing off against new threats.