Another plot could be set in a post - war scenario. The Autobots are rebuilding their world, and Optimus Prime and Arcee are tasked with different aspects of the reconstruction. However, they keep finding excuses to work together. As they do, they gradually fall in love while also dealing with the trauma of the war and the challenges of creating a new future for their kind.
A great plot could involve Arcee getting injured during a fight and Optimus Prime having to protect her while she recovers. During this time, they could have deep conversations about their hopes for the future of their race. Or perhaps there's a fanfic where they discover an ancient artifact that has a connection to both of their pasts, and they have to work together to unlock its secrets.
Perhaps a fanfiction where Arcee and Optimus are transported to an alternate dimension. In this new world, they have to figure out how to get back home while also dealing with the strange new rules and inhabitants. They might find that their relationship is put to the test as they face unfamiliar and often dangerous situations. They could also learn new things about each other that they didn't know before.
A really interesting plot could be set in an alternate universe where Bumblebee and Optimus Prime are not part of the Autobot - Decepticon war. Instead, they are explorers. They could encounter a strange new planet or a powerful ancient artifact that tests their relationship and their understanding of each other. This would be a great opportunity to explore their characters outside of the typical war - torn setting.
One plot idea could be that Optimus Prime and Starscream are forced to team up during a crisis that threatens both Autobots and Decepticons. They start to see each other in a new light and develop an unlikely friendship. Another could be a story where Starscream is injured and Optimus Prime has to make the choice between helping him or leaving him to the mercy of other Decepticons. This could lead to a complex relationship between them. A third idea is a time - travel plot where they end up in an alternate universe where their roles are reversed and they have to figure out how to get back to their own universe while dealing with their changed relationship.
There could be a fanfiction where a strange energy source affects Optimus Prime and Megatron, causing them to swap personalities or abilities. This would be a humorous yet also thought - provoking plot. They would have to navigate their new selves while still trying to lead their factions. The Autobots would be confused by an aggressive Optimus and the Decepticons would be equally bewildered by a more pacifist Megatron.
Romance is also a theme, though it can be a bit tricky in the context of Transformers. Writers often explore the emotional connection between Arcee and Optimus Prime, how they might have a deeper understanding of each other that goes beyond just comradeship.
One great fanfiction could be about Optimus and Arcee going on a dangerous mission together. They face numerous challenges, like battling a powerful new Decepticon. Their teamwork and trust in each other are put to the test. Arcee's speed and agility combined with Optimus' strength make them a formidable duo. Along the way, they might have some deep conversations about the future of their race and their place in the war.
One possible plot could be that during a dangerous mission, Optimus Prime and Arcee get separated from the rest of the team. As they struggle to survive and find their way back, they rely on each other more than ever. This shared experience deepens their bond, and eventually, they share a kiss as a sign of their new - found closeness.
One idea could be that Optimus Prime somehow ends up in the RWBY universe and teams up with Team RWBY to fight a common enemy. Maybe a new type of Grimm that is attracted to his Cybertronian energy.
One plot idea could be that Megatron and Optimus Prime are forced to team up in an alternate dimension. They have to put aside their differences to face a common enemy that is threatening the very fabric of that dimension. Maybe it's an ancient evil that has the power to destroy all Cybertronians.