A great plot could be that a virus in the sas zombie assault world mutates and starts affecting not just humans but also the environment. The SAS has to collaborate with a group of scientists from a crossover universe. The scientists have advanced technology or knowledge that might help stop the virus. Along the way, they face challenges like zombie - animal hybrids and have to adapt their combat strategies accordingly.
Well, perhaps in the fanfiction, the SAS discovers a portal that leads to a different dimension full of zombie - like creatures but with unique abilities. They then have to use their military skills combined with the knowledge they gain from the new environment to survive and close the portal. They could encounter some local resistance fighters in that dimension who are also trying to fight the zombies, and they all join forces.
How about including some characters from the Left 4 Dead series? The survivors in that game have a lot of experience fighting zombies in different environments. They could work together with the SAS in the crossover fanfiction. For example, Zoey could use her street - smart skills, and Louis could contribute his knowledge of finding supplies in urban areas. And of course, the Special Infected from Left 4 Dead could add more danger and variety to the zombie threats in the story.
One idea could be that Bella, instead of becoming a vampire, is bitten by a zombie. She then has to struggle with her new zombie nature while still holding onto her humanity. For example, she might try to resist the urge to attack her human friends like Jacob and Charlie.
One idea could be exploring the backstories of the lesser - known characters in the 'Batman Assault on Arkham' universe more deeply. For example, you could focus on Killer Croc's life before Arkham and what led him to become the way he is. Another plot could involve a team - up between unexpected characters from the movie, like Harley Quinn and Deadshot, against a new threat in Arkham that the Bat - family is unaware of.
One idea could be exploring the backstory of the antagonists in more detail. Maybe there's a hidden motive or a tragic past that led them to oppose Star Fox. Another could be a story where the Star Fox team has to deal with a new, unexpected threat that is even more powerful than the usual foes they face. And a third idea is a story centered around a character from the team having to make a difficult personal sacrifice for the greater good of the galaxy.
One idea could be to focus on a new alien species attacking Moya. The crew has to quickly figure out the aliens' weaknesses and form alliances with other races they encounter in the Uncharted Territories. Another could be an internal 'assault' within the crew, like a conflict over resources that threatens to tear the group apart. Or perhaps a mind - control plot where an enemy assaults the minds of the crew members one by one.
One idea could be that a zombie virus spreads in the Naruto world. Naruto and his friends have to not only fight the zombies but also figure out how the virus started. Maybe Orochimaru was experimenting with dark jutsu and it went wrong.
One idea could be a gamer who uses their in - game survival skills to lead a group in the real - world zombie apocalypse. For example, they know how to scavenge for resources just like in the games they play.
One idea could be a group of survivors who are all musicians. They use their music to communicate with other groups across the apocalyptic landscape and also to keep their spirits up. Another could be a story where the zombies start to regain some of their humanity and the survivors have to decide whether to trust them or not. Maybe a story about a scientist in the group who is trying to find a cure using only the limited resources they have.
One possible plot could be that a powerful necromancer from the Naruto world accidentally unleashes a zombie plague. Naruto and his friends have to not only fight their zombified comrades but also find a way to reverse the spell. They could use their ninja skills in unique ways, like using shadow clones to distract the zombies while they search for a cure.
Maybe a crossover with a magical anime. The nanbaka characters could suddenly find themselves in a world full of magic. Some of the nanbaka characters might be really good at using magic in unexpected ways, like Jyugo using his shackles in a magical battle.