One idea could be a crossover with another popular military - themed game. For example, characters from Modern Warfare teaming up with those from Battlefield. They could face a common enemy that threatens global security. This would bring together different combat styles and weaponry.
A crossover with a science - fiction franchise like Halo might be cool. Imagine Modern Warfare soldiers encountering the Covenant. The soldiers would have to adapt their tactics to deal with the advanced alien technology. It could involve a lot of high - stakes battles and strategic planning.
Another plot idea could be a crossover with a post - apocalyptic game like Fallout. Modern Warfare characters could find themselves in a world ravaged by nuclear war. They would have to deal with new threats like mutated creatures while also trying to find a way to restore order in this chaotic new world.
One idea could be to have the RWBY characters adapt to modern warfare weapons and tactics. For example, Ruby could use her speed with modern sniper rifles. Another idea is to create a scenario where they have to fight against a new type of Grimm that is influenced by modern military threats. Or perhaps a story where they team up with modern military forces to take on a common enemy.
A cool plot could involve a crossover with the 'Alien' franchise. The soldiers in Call of Duty Advanced Warfare could be sent to a distant planet where they encounter the deadly Xenomorphs. They would have to use their advanced military skills and weaponry to survive against these terrifying creatures. It could also be interesting if there was a crossover with a post - apocalyptic game like 'Fallout'. The Advanced Warfare characters could end up in the wastelands of 'Fallout', trying to adapt to the new environment and find a way back to their own world while dealing with the various threats in the Fallout universe.
Another idea is to explore the backstories of the existing characters in more depth. For example, you could write a fanfic about how a certain character got their special skills or what their life was like before joining the military. This can add a lot of richness to the overall understanding of the game's characters.
Another option is a crossover with the Pokémon world. The Phantom Thieves could travel to a region in the Pokémon world and discover that someone is using Persona powers to make Pokémon act out of control. They would need to catch Pokémon themselves and use their combined powers of Personas and Pokémon to stop the bad guy. It would be interesting to see how they interact with Pokémon trainers and the whole Pokémon ecosystem.
A cool plot could involve the Persona 5 crew going back in time to the events of Persona 3. They might end up interfering with some of the original events, which could have unforeseen consequences. For example, they could accidentally change the way a key character in Persona 3 awakens their Persona, and then have to figure out how to fix it while also dealing with the Shadows in that era.
One idea could be to cross it with another popular RPG. For example, having the Persona 4 characters enter the world of Final Fantasy. They could interact with the different races and magic systems there. Another could be a crossover with a detective - themed anime. The Investigation Team could team up with the detectives from that anime to solve a mystery that spans both worlds.
Another plot could involve a crossover with the Punisher and the X - Men. Frank Castle might find himself in a situation where he has to work with mutants. He could initially be distrustful but then realize they are fighting for a similar cause against a common enemy that is targeting both humans and mutants. For example, a group of anti - mutant and anti - vigilante fanatics.
One idea could be a crossover with Peter Pan. Tinkerbell could meet characters from another world, like Alice from Wonderland. She might be confused by the strange rules and creatures there, and her magic could interact in unexpected ways with the Wonderland magic.
Another plot could involve a crossover with a post - apocalyptic world. The Boys find themselves in a world where society has collapsed, and they have to team up with the survivors against new threats. This could bring out new sides of the characters as they are forced to adapt to a completely different environment and face challenges they've never faced before.
One idea could be to cross over the characters from 'Percy Jackson and the Olympians' with those from 'The Kane Chronicles'. For example, the demigods and the magicians could team up to fight a common enemy that threatens both the Greek and Egyptian mythological worlds. Maybe a new dark force that has the power to disrupt the balance between the two realms.