Maybe in the fan fiction, the Ghostbusters are called to an old, haunted mansion that has a portal to another dimension full of extremely powerful ghosts. They need to not only deal with the ghosts coming through but also find a way to close the portal. This could involve a lot of research and some new, experimental equipment.
Another plot could be that a new member joins the Ghostbusters. This person has a special ability to communicate with ghosts in a way that no one else can. But they are also a bit of a wildcard. The story could be about how the team adjusts to this new addition and how they use this new ability to solve some really tough ghost - related problems.
One idea could be that the Ghostbusters discover a new type of ghost that can possess technology. So they have to find a way to stop it from taking over all the electronics in the city. It would be a race against time as the city starts to descend into chaos with machines going haywire.
A plot could be that the female Ghostbusters are sent to an old, abandoned amusement park. The ghosts there are the spirits of former employees and visitors who died in freak accidents. The Ghostbusters have to figure out how to calm the ghosts and send them to the other side without destroying the park, which has historical significance.
One idea could be a new type of ghost that is immune to the traditional proton packs, forcing the Ghostbusters to develop a new technology. Another could be a story where the Ghostbusters are transported to an alternate dimension full of super - powerful ghosts. Or perhaps a plot where a former Ghostbuster returns as a ghost himself, causing moral and practical dilemmas for the team.
Another plot could involve a crossover with 'Men in Black'. The two groups could initially be at odds as they deal with different types of 'paranormal' entities. But then they discover a common threat that is both extraterrestrial and ghost - like. They have to combine their resources, the Ghostbusters' knowledge of the spirit world and the Men in Black's expertise in dealing with aliens, to save the world from this new and dangerous entity.
A more character - driven plot for the fanfiction could be about one of the kids in Ghostbusters Afterlife struggling with the responsibility of being a Ghostbuster. They might feel like they're not living up to the legacy of their family. Through a series of events, they overcome their self - doubt and prove themselves to be a worthy part of the Ghostbusting team.
One plot idea could be a female Ghostbuster who discovers a new type of ghost that is only visible to women. She has to convince her male colleagues to believe her and then figure out how to catch it. Maybe this new ghost is causing strange phenomena in a women - only area like a women's college dormitory.
Some interesting Ghostbusters fanfiction concepts could be centered around the ghosts themselves. For instance, a story where a particular ghost has the ability to possess inanimate objects and uses this power to create chaos in the city. The Ghostbusters would then have to figure out how to stop it without causing too much destruction. Another concept could be a time - travel fanfiction where the Ghostbusters go back in time to prevent a major ghost - related disaster from ever happening. This could involve meeting their younger selves or influencing key events in the past related to the supernatural.
One idea could be to explore the backstories of the Ghostbusters' equipment. For example, how Egon came up with the design for the proton packs. Another could be a story where the Ghostbusters have to deal with a powerful ghost from another dimension that has unique abilities they've never faced before. Maybe a story about the team's early days, when they were just starting out and trying to get their business off the ground.
Maybe an OC who is an international Ghostbuster, coming to the 2016 team with different techniques and cultural beliefs about ghosts. This OC could introduce new ways of dealing with ghosts that are based on ancient traditions from their home country, causing some interesting clashes and also new learning experiences for the whole team.
One idea could be that a portal between the Ghostbusters' New York and the Gargoyles' world has opened up. Ghosts start pouring into the Gargoyles' domain, causing all sorts of problems for them. The Gargoyles seek out the Ghostbusters for help. As they work together, they discover that there is a deeper mystery behind the portal's opening, something that ties into the ancient history of both their worlds.
One idea could be a story where the Mandalorian has to team up with an old enemy to fight a new, greater threat. Maybe a powerful Sith Lord emerges and they have to put aside their differences.