Warhammer 40k and Star Wars Crossover Fanfiction: What are some interesting plot ideas?

One interesting plot twist could be the combination of the Force from Star Wars with the psychic powers in Warhammer 40k. Imagine a Jedi using his Force powers in the grim and dark universe of 40k, facing off against Chaos psykers. Another could be the appearance of Imperial Stormtroopers in a Warhammer 40k battle, their white armor standing out among the chaos. Maybe they could be mistaken for some sort of new xenos threat at first. And a third plot twist might be the discovery of a lost Star Wars planet in the Warhammer 40k galaxy, full of unique technology and species that both sides would be eager to control or destroy.

Another interesting concept is a crossover during a time of great chaos. For example, the warp rifts in Warhammer open up near a key Star Wars system. This causes all kinds of chaos as the daemons from Warhammer pour into the Star Wars universe, and the various factions in Star Wars have to figure out how to deal with these otherworldly threats. It could also explore how the Jedi might try to use the Force to combat the daemonic influence.

Perhaps a Dark Eldar wych could form an unlikely alliance with a Space Marine. Maybe the wych has a personal vendetta against a chaos warband that is also targeting the Space Marine's chapter, and they decide to work together to take down the common enemy. This would involve a lot of tense moments as they try to trust each other despite their very different cultures and motives.

One idea could be a crossover with the Star Trek universe. The Tyranids could be seen as an extremely hostile alien force that the Federation has to deal with. Their bio - ships and swarming tactics would be a huge contrast to the more technological - based Starfleet.

One idea could be a crossover with Star Wars. Imagine the Imperium of Man encountering the Galactic Empire. The two totalitarian regimes could have some intense ideological battles and epic space battles as well.

One interesting concept could be the clash of different ideologies. In Warhammer 40k, there is a lot of grimdark and a strict hierarchy, while Star Trek is more about exploration and unity. So seeing how characters from both universes react to the other's values can be really engaging.

One idea could be a vampire Space Marine. Maybe a genetic experiment gone wrong in the Imperium that results in a Marine with vampiric traits. He has to struggle with his newfound thirst while still trying to fulfill his duty to the Emperor.

One idea could be the Imperium of Man encountering the Citadel Council. The Imperium's strict dogma and military might would clash with the Council's more diplomatic approach. For example, the Space Marines might be seen as terrifying super - soldiers by the Mass Effect races.

A great plot could be that Master Chief somehow gets transported to the Star Wars universe. He could find himself in the middle of a battle between the Sith and the Jedi. His combat skills and advanced armor would be a huge asset to either side. Or perhaps there could be a story where the Forerunners have some ancient connection to the Force in the Star Wars galaxy. This could lead to a search for lost Forerunner technology that could change the balance of power in the Star Wars universe.

Perhaps in a Star Wars Twilight crossover fanfiction, the Force could be seen as a kind of super - power in the Twilight universe. A Jedi could come to train the Twilight characters in how to use this 'new' power. They would have to adapt their Jedi teachings to fit the different nature of the Twilight world, which has its own set of rules regarding vampires and werewolves.