Well, perhaps in the fanfiction, Edward is kidnapped by a secret organization that wants to use his knowledge of the military's alchemical operations. They might hold him captive in an underground lair, filled with strange alchemical contraptions. Or maybe he's kidnapped by a jealous alchemist who feels overshadowed by Edward's fame. This alchemist could try to steal Edward's research and take credit for his work. Also, it could be that an otherworldly being kidnaps him to learn about human alchemy.
In some fanfiction, Edward could be kidnapped by a group of anti - alchemist extremists. They see him as a symbol of all that's wrong with alchemy and plan to publicly execute him to send a message. Another interesting plot would be if he's kidnapped by a time - traveling alchemist from the future. This alchemist knows that Edward will cause some great catastrophe in the future and tries to stop it by holding him captive. Additionally, Edward might be kidnapped by a powerful alchemist who wants to use his body as a vessel for a dark alchemical ritual.
Well, a plot could involve Edward being betrayed by a mentor figure. This person could have been guiding him in alchemy all along but has a hidden agenda. Maybe they want to use Edward's unique alchemical abilities for their own dark experiments. Or, in a different scenario, Edward could be betrayed by a love interest. She might pretend to love him while actually spying on him for an opposing force, stealing his secrets and leaving him heartbroken and in a difficult situation.
Well, perhaps in the fanfiction, Edward's sacrifice causes a rift in the fabric of time. This rift then starts to distort reality, and it's up to his friends to figure out how to fix it. They have to journey through different time periods and face challenges that Edward had faced before. Or it could be that his sacrifice was misinterpreted by some, and they start to view alchemy as a dangerous art again, leading to a conflict between those who understand the true meaning of Edward's sacrifice and those who don't.
A crossover with the world of Attack on Titan could be interesting. Female Edward could use her alchemy to help in the fight against the Titans. Maybe she could create new weapons or defenses using her alchemical knowledge. And her relationship with the Survey Corps members would be a great source of character development.
A really interesting plot could be a time - travel scenario. Chimera Mustang and Edward Elric get sent back in time to a crucial point in the history of alchemy. They have to navigate this new - old world while also trying not to change history too much. This would be full of opportunities for them to interact with past versions of characters and maybe even prevent some future disasters.
In this fanfiction, her role as an alchemist might be perceived differently. As a girl, she might face more discrimination in the male - dominated field of alchemy. This could lead to stories of her having to prove herself more often and in different ways than in the original story.
One idea could be a crossover where Edward and Urahara meet in a world that combines their respective universes. They could exchange knowledge about alchemy and spiritual powers. For example, Edward could be intrigued by Urahara's zanpakuto and its unique abilities, while Urahara might be interested in the principles of alchemy.
A possible plot is that Shikamaru is kidnapped by a rival village that believes his strategic mind can give them an edge in an upcoming war. His kidnappers try to brainwash him into working for them. However, Shikamaru uses his wits to resist and also leaves subtle clues for his comrades to find him. His friends, on the other hand, must infiltrate the rival village without getting caught to rescue him.
One idea could be that MacGyver is kidnapped by a group who wants him to build a dangerous weapon for them. He has to use his wits and the limited resources in his captivity to not only escape but also prevent the weapon from being built. Another plot could involve MacGyver being kidnapped by a rival agency who wants to steal his secrets and tradecraft. He then has to outsmart them by creating diversions and makeshift tools within the confined space. A third idea is that he is kidnapped by someone seeking revenge for a past mission gone wrong, and he has to convince his captor of his innocence while finding a way to break free.
One idea could be that Legolas is kidnapped by an old enemy of the elves. This enemy might want to use Legolas as a bargaining chip to get some powerful elven artifact. Another plot could involve a powerful dark magic user who kidnaps Legolas to drain his life force which is believed to be very strong due to his elven heritage. A third option is that he is kidnapped by a group who mistakes him for someone else who has great value to them.
One interesting plot idea could be that Roy and Edward have to team up on a secret mission that involves alchemy and military strategy. They start off not getting along well because of their different personalities and approaches, but as the mission progresses, they learn to respect each other and become friends. Another idea is that Edward discovers a new form of alchemy that Roy is interested in for military use, and they have to work together to keep it from falling into the wrong hands.