One potential storyline could be that the alchemists in Full Metal Alchemist somehow stumble upon the world of Mushishi. Maybe they are on a quest for a rare ingredient or to study a unique form of alchemy. In this new world, they encounter the Mushishi, who have their own set of rules and powers regarding the Mushi. The two groups could initially be at odds, with the alchemists' scientific approach clashing with the more spiritual and natural approach of the Mushishi. But as the story progresses, they might find common ground in their pursuit of understanding the mysteries of their respective worlds.
The alchemists' ability to transmute matter could be combined with the Mushishi's ability to interact with the Mushi. For instance, an alchemist could transmute a substance to create a container or tool that can better detect or contain the Mushi. The Mushishi, in turn, could use their understanding of the Mushi to guide the alchemist in what kind of transmutation would be most effective. For example, if a particular Mushi is attracted to a certain type of metal, the Mushishi could inform the alchemist, who could then transmute that metal into a trap.
One common storyline could be the reborn male's struggle to adapt to the world of Full Metal Alchemist. He might have memories from his past life that conflict with the new reality he's in. For example, he could remember certain events that haven't occurred yet in the FMA timeline and try to prevent or change them. Another could be his journey to master alchemy in a new and different way compared to the original characters. He may discover unique alchemical techniques that are a result of his rebirth and his knowledge from another life.
One idea could be a crossover with the Harry Potter universe. Edward and Alphonse could attend Hogwarts and learn about magic while also trying to find a way to use alchemy in that world. Maybe they'd be interested in the Philosopher's Stone in the Harry Potter series, which has similarities to the concept of the Philosopher's Stone in Full Metal Alchemist.
Shamballa in 'Full Metal Alchemist' is a concept that ties into the complex world of alchemy. It is a place that seems to hold great power and knowledge. The story may involve characters trying to unlock the secrets of Shamballa, which could be related to the true nature of alchemy, the origin of certain elements in their world, or even a way to transcend the normal limitations of their reality. It adds an element of mystery and a greater purpose to the overall narrative of the series.
The story of Full Metal Alchemist explores themes like redemption, sacrifice, and the consequences of playing with forbidden alchemy. It's a deep and complex tale.
There could be a storyline where an evil force has brainwashed some of the Justice League members, and Spider - Man has to figure out a way to break the spell. Along the way, he teams up with the unaffected members like Wonder Woman. This would show his intelligence and resourcefulness. Also, a story where Spider - Man accidentally ends up in the Justice League's universe and they have to work together to get him back home while also dealing with threats in their world.
One idea could be that the main character is reborn as an alchemist with a unique ability that was never seen before in the Full Metal Alchemist world. For example, the ability to transmute emotions into physical forms. This could lead to a whole new set of adventures and challenges as they try to understand and control this power while also dealing with the existing threats in the FMA universe.
The fanfic might also focus on the relationships between the characters in a more in - depth way. It could show the bond between the Elric brothers in a different light, perhaps under extreme pressure. It could also explore the relationships between the military characters and how they interact when pushed to their limits at the 'Breaking Point'.
In many Full Metal Alchemist fanfics about Ed and Winry, their relationship is often deepened and explored in unique ways. Some fanfics might focus on their childhood bond and how it evolves as they grow older. Ed's journey as an alchemist and Winry's skills as an automail mechanic can play important roles in these stories. For example, Ed might rely on Winry's automail repairs not just physically but also emotionally, seeing her as a constant in his tumultuous alchemist life.
First, you need to understand the rules of both universes involved. For example, if it's a crossover with Star Wars, you have to know how the Force works in Star Wars and how alchemy functions in Full Metal Alchemist. Then, find a common ground. Maybe there's a similar power source in both worlds that can be the starting point for the plot. Like a dark energy in Star Wars and a corrupt form of alchemy in Full Metal Alchemist.