Another possible main character could be an alien from Earth itself. This character could be the one to introduce the alien culture and technology to the RWBY world. They could be a sort of guide for the RWBY team, helping them understand the intentions of the other aliens and also teaching them new things that could be useful in their fight against the Grimm and other threats in Remnant.
Ruby Rose could definitely be one of the main characters. Her leadership skills and curiosity would make her interested in these aliens from Earth. She might be the one to initiate contact or try to understand their motives.
Well, it could be about a group of RWBY characters encountering aliens that are from Earth but have some unique abilities or cultures. Maybe these aliens have been hidden on Earth all this time and their presence starts to disrupt the balance in Remnant. The RWBY team then has to figure out how to deal with them, whether it's through negotiation or combat.
Well, aside from the RWBY team and their associated characters, it's possible that some original Earth characters could become main characters too. For example, a scientist who discovers the Remnant beings and helps them understand Earth technology, or a street - smart kid who shows the RWBY characters the ropes in a big city. These new characters could bring fresh perspectives and new storylines to the fanfiction.
For a 'rwby megatron fanfiction', Ozpin could be a main character. He has a lot of knowledge and could potentially figure out a way to deal with Megatron. The RWBY girls would also be main characters as they are the heroes of their world. Megatron would be the main antagonist, driving the conflict in the story with his desire for power and domination.
Ruby's adventurous spirit would lead her to explore every aspect of the Earth military in the fanfiction. She would be like a kid in a candy store, especially when it comes to high - tech weapons. Weiss's personality of being a bit haughty initially would make her a bit of a snob towards the Earth military, but her intelligence would make her soon understand their importance. Blake's withdrawn nature would mean she would be in the background, but her thoughts would be deep as she compares the military to the power dynamics in Remnant. Yang's exuberance and love for a good fight would have her eager to see how strong the Earth military really is.
Blake would be a likely main character. As a Faunus herself, she could play a crucial role in guiding Cardin through his new identity. She could share her own experiences of discrimination and help him understand the importance of the Faunus cause. Maybe they could work together to expose some anti - Faunus groups operating within the school or the city.
Yang is also a fan favorite. Her brawler - like fighting style and her strong - willed nature can lead to some great interactions in the 'rwby vs earth' setting. She could get into some interesting battles or rivalries with Earth characters.
The Earth Soldier protagonists themselves can be very popular. Fans like to create unique backstories for them, like they were part of a special military unit on Earth before ending up in the RWBY world. Their different fighting styles and personalities draw readers in.
Blake Belladonna is another character that often features prominently in fanfiction. Her complex backstory, especially her past with the White Fang, can be explored in new ways when combined with the concept of Remnant and Earth. Whether she's on Earth learning about different forms of equality or teaching Earthlings about the Faunus on Remnant, she's a great character for fanfiction.
New students from different kingdoms could also be main characters. For instance, a student from Vacuo who has a unique sand - based fighting style. Or a student from Atlas who is a tech genius and uses advanced weapons. They could team up with the descendants of Team RWBY to form a new, diverse team.
Obviously, the members of Delta Squad would be main characters. They'd bring their own personalities and abilities to the story.