One idea could be that the Spartans from Halo and the Witches from Strike Witches team up to fight a common alien threat that has invaded both of their universes. The Spartans' advanced weaponry and combat skills combined with the Witches' magical abilities would make for an epic battle.
Perhaps a scenario where a Halo technology gets mixed up with the Strike Witches' world. For example, a Covenant energy source ends up in the Strike Witches' world and starts causing strange magical disruptions. The Witches then have to work with Halo characters who understand the technology to fix it.
A story could be about a Witch who gets lost in the Halo universe. She has to quickly adapt to the more militaristic and high - tech environment. Along the way, she meets Master Chief and they form an unlikely alliance. She uses her magic in unique ways to help him in his missions against the Covenant.
The Arbiter and Perrine - H. Clostermann. The Arbiter is a complex character from the Halo universe with his own code of honor. Perrine is a proud and strong - willed Witch. Their different cultures and values could lead to some great character development moments as they work together, whether they initially get along or not.
One possible plot could be that the ninjas from Naruto world discover the existence of the Strike Witches. They could initially be in conflict due to differences in their fighting styles and goals. But then, they realize they have a common enemy, like an ancient dark force that threatens both their worlds. They then combine their powers, with the Naruto characters using their jutsus and the Strike Witches using their magic and flight abilities to fight this new threat.
One idea could be exploring the backstories of the individual witches more in - depth. For example, how they first discovered their powers and what their lives were like before joining the fight. Another could be a story about a special mission that the witches have to undertake behind enemy lines, filled with danger and unexpected alliances.
One idea could be that the Servants from Fate are transported to the Halo universe. For example, Saber could find herself in a battle against the Covenant. Her noble phantasm could be a powerful weapon against the alien foes. Another plot could involve Master - Spartan team - pairings. A Spartan could be paired with a mage to fight a common enemy that threatens both the Halo and Fate worlds.
One idea could be a Spartan from Halo ending up on Pandora. Maybe they team up with the Na'vi to fight off a common enemy, like a new type of alien that's more powerful and dangerous than the Covenant or the RDA. The Spartan could introduce advanced human technology to the Na'vi, which would change their way of life in some aspects. For example, they could use some of the shielding technology to protect their homes. Another plot could involve the transfer of consciousness, like in Avatar, but with a Halo - related twist. Perhaps a character's mind is transferred into an enhanced alien body, similar to the Elites in Halo.
One idea could be that the Master Chief is somehow transported to Skyrim. He might use his advanced combat skills and technology to deal with the dragons. For example, his energy shields could protect him from dragon fire. Another plot could involve the races in Skyrim getting access to Halo's weaponry and having to figure out how to use it. Maybe the Dwemer could reverse - engineer Covenant weapons.
Maybe in the fanfiction, Cortana could be integrated into Iron Man's suit. Her advanced AI could enhance the suit's capabilities even further. And they could work together to take on a new villain that is causing chaos in both the Halo and Marvel worlds. It would be a great mix of science - fiction elements from both universes.
One idea could be that Naruto characters are teleported into the Halo universe. They might use their ninja skills to fight the Covenant. For example, Naruto could use his shadow clone jutsu to confuse the enemy, while Sasuke could use his Sharingan to predict their moves. Another plot could involve Master Chief getting some of Naruto's chakra abilities, making him even more powerful in combat against the Flood.
Another plot could involve Noble 6 having their consciousness transferred into a Forerunner construct in a crossover. This would force them to navigate Forerunner technology and politics while still trying to uphold their UNSC values. They could form an unlikely alliance with a Forerunner AI to stop a rogue element within the Forerunner society.
How about a story where Moi discovers a long - lost magic technique. Minna is intrigued but also a bit jealous. This causes some tension between them. However, an enemy attacks the Strike Witches and they quickly realize they need to work together. Moi tries to teach Minna the new technique but it's difficult. As they practice, they start to communicate better and Minna finally masters it. With their combined powers and the new technique, they are able to defeat the enemy and their relationship becomes stronger than ever.