Another interesting concept is a crossover with a superhero universe. Picture the Puella Magi joining forces with the Avengers. They would bring their own brand of magic to the superhero battles, and there could be interesting interactions between the different power sets and personalities.
You could do a Magi crossover with 'Fairy Tail'. The guild system in Fairy Tail and the different types of magic there could be compared and contrasted with Magi. The characters from both could team up for quests. Or consider a crossover with 'Attack on Titan'. The Titans could be a new threat in the Magi world, and the Survey Corps could use Magi's magic to fight them.
Another plot could involve Homura traveling to the Miraculous Ladybug universe. She could initially be suspicious of the heroes there because of her experiences in her own world. However, as she sees how Ladybug and Chat Noir operate and their pure intentions, she decides to help them against a common enemy that is threatening both universes. This would create an interesting dynamic as Homura's more cynical and strategic approach clashes and then blends with the more light - hearted and hopeful nature of the Miraculous heroes.
First, decide which other universe or series you want to cross over with. Then, research both 'puella magi' and the other element thoroughly. This helps you understand the characters, settings, and rules of both.
An interesting idea could be a time - travel fanfic where Sayaka goes back in time and tries to prevent some of the tragedies that happened to them. She teams up with Kyoko in the past, and together they try to change the course of events. This would allow for a lot of character development as they interact with their past selves and try to make different choices.
One idea could be a crossover with a popular fantasy world like Middle - earth. Magi from Magi Nation could travel to Middle - earth and interact with the races there, perhaps helping in the fight against Sauron. Another could be a crossover with the Pokemon universe, where Magi use their magic to communicate with Pokemon and go on adventures together. And a third idea is a crossover with the Harry Potter world, with Magi attending Hogwarts and sharing their unique magical abilities with the wizards there.
One idea could be a crossover with 'Fairy Tail'. The powerful magic in 'Fairy Tail' and the unique magic system in Magi could create really cool battles and interactions. For example, the mages from 'Fairy Tail' could team up with the Magi characters to fight a common enemy like an ancient evil djinn. Another idea is a crossover with 'Naruto'. The shinobi skills in 'Naruto' and the magic in Magi could be combined in interesting ways. Maybe a Magi character could learn some ninja techniques or vice versa. And a crossover with 'One Piece' would also be great. The Straw Hat Pirates could visit the world of Magi and get involved in the search for dungeons and treasures there.
One plot idea could be that the male OC is a transfer student who has a hidden past as a magical boy from another city. He has different rules about magic compared to the girls in Madoka's town. Another idea is that he is on a mission to break the cycle of the magical girl system from the inside. He tries to convince the girls to stop making contracts without sacrificing themselves.
One idea could be that the characters from Fairy Tail and Magi team up to defeat a common, extremely powerful dark magic user. The mages from Fairy Tail could use their unique magic skills like Natsu's fire magic, while the Magi characters could utilize their dungeon - conquering abilities and djinn powers. For example, Alibaba could use Amon's power in combination with Gray's ice - make magic to create some really cool and powerful attacks.
The 'puella magi madoka magica wraith arc light novel' is important as it likely expands on the story. It might introduce new plotlines related to the wraiths, which are a key part of the Puella Magi Madoka Magica universe. It could also provide more in - depth character development for the magical girls.
One idea could be a fanfic where the main characters from Magi are transported to a modern-day world. They would have to adapt to new technologies and cultures while still maintaining their magical abilities. For example, Alibaba could use his swordsmanship in a modern-day martial arts tournament. Another idea is a prequel fanfic that explores the backstories of the different djinns and how they came to be in the Magi world. It could also show the relationships between the djinns and the first magi who summoned them.