A cool plot could be Edward getting involved in a political intrigue in this new world. Since he has a strong sense of justice from his own world, he might find himself in the middle of a power struggle between different factions. He could use his wits and knowledge from his home world to try and bring about a positive change in this new and unfamiliar political landscape.
Another plot might involve Edward meeting alternate versions of his friends and family from Fullmetal Alchemist in this other world. This could lead to some really emotional and thought - provoking moments as he has to come to terms with how different they are while still seeing the similarities. Maybe he meets an Alphonse who is not a suit of armor but a normal human, and they have to re - establish their bond.
One interesting plot could be Edward trying to adapt to a world where alchemy doesn't exist in the same way. He might have to learn new forms of magic or technology to get by. For example, he could struggle with not having his alchemy skills to help him in combat or solve problems at first, but then gradually discovers new powers within himself in this new world.
Well, perhaps there's a plot where Edward, as a girl, has to keep his true identity a secret. This could lead to some really tense and comical situations. Like when his friends from before start showing different kinds of interest in him, not knowing it's really Edward. And he has to figure out how to interact with them without giving away his secret while also trying to find a way to turn back into his original self.
One interesting plot could be where Edward has to adjust to sudden fatherhood while still dealing with his alchemical pursuits. Maybe he discovers a new form of alchemy related to protecting his child.
One more great plot could be Naruto being trained by Edward in alchemy. Edward is a brilliant alchemist despite his young age. Naruto, with his eagerness to learn new things, would soak up all the knowledge. He could start creating his own alchemical ninja tools. For example, he could make a kunai that can transmute into different forms depending on the situation. And as he gets better at alchemy, he might start to question his own ninja way. Is it really all that different from alchemy? This internal struggle could add a lot of depth to the fanfiction.
Winry Rockbell is often paired with Edward. Their relationship from the original series can be further explored in the alternate world setting. Maybe in this new world, they have different challenges in their relationship, like different social statuses or new enemies that target their relationship.
Another plotline might involve Edward reuniting with his old friends and family. There could be emotional reunions and then they all team up to face a new, greater threat together. They might have to overcome past misunderstandings and grow stronger as a group. For example, Edward could find that his brother Alphonse has developed in unexpected ways while he was away, and they have to readjust to each other.
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.
The challenges she faces can also be different. In the original story, Edward had his own set of difficulties as a male alchemist. As a female, she might face additional discrimination or different expectations in the world of alchemy. Fanfictions can explore how she overcomes these new challenges while still trying to achieve her goals like getting their bodies back (if following the main plot of the original story).
Some fanfictions might explore the concept of Edward being protected by an angel. The angel could be a new character or perhaps an existing character from the series in an angelic form. This protection could be due to a prophecy or because Edward has some special role to play in the grand scheme of things related to the angelic realm.
One interesting story could be where Edward uses his alchemy skills in a unique way related to milk. Maybe he discovers a new alchemical property of milk that helps him in his quest. For example, it could be a story where he uses milk to create a special potion that gives him temporary enhanced strength.
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.