One interesting concept could be the magical girls in the Star Wars universe. Imagine them using their magic to fight Sith Lords or help the Jedi. For example, they might use their powers to enhance lightsaber combat or to sense the Force in a new way.
Some Madoka Magica OC fanfictions explore the idea of an OC coming from a different magical realm. This OC could introduce new magical rules and cultures, which would be really fascinating as it would contrast and interact with the known Madoka Magica magic system.
Homura could be a great main character. She could be a Jedi - like figure, using her time - looping abilities in a way similar to how a Jedi uses the Force. She might be on a quest to save Madoka, who could be a powerful Force - sensitive being in this fanfic.
A really interesting concept could be the idea of redemption in a 'madoka magica x steven universe fanfic'. In Madoka Magica, there are characters who make desperate choices, and in Steven Universe, there is a strong theme of forgiveness and growth. Maybe a character from Madoka Magica who has made a dark choice could find a path to redemption with the help of the positive and inclusive ideology of the characters in Steven Universe.
One interesting concept is exploring the backstories of minor characters. For example, in some fanfictions, they might delve into the past of a random stormtrooper, showing how they ended up in the Empire. Another concept could be alternate endings to major events in the series. It gives fans a chance to rewrite parts they thought could have been better.
One popular trope is the 'time - loop fix - it' where Homura uses her time - looping abilities to try and create a perfect situation for Madoka. This often involves Homura going through multiple loops, each time learning more about Madoka and how to protect her better.
Another theme is time - related. Since Homura has the ability to manipulate time in the show, many fanfictions play with this concept in relation to her relationship with Madoka. For example, stories might involve Homura going back in time to save Madoka in different ways or dealing with the consequences of her time - traveling on their relationship.
In Madoka x Homura fanfiction, the power dynamics between them can be an interesting aspect. Madoka, as a very powerful magical girl, and Homura, with her time - looping abilities, have a unique relationship. Fanfiction could play with how they use their powers in relation to each other. Maybe in a fan - created scenario, they combine their powers to save a new threat that wasn't in the original series.
Some of the best Madoka Magica fanfics include 'Soul Gems Reforged'. This fanfic explores the concept of soul gems in a new light, with a plot that involves trying to find a way to purify them without the need for sacrifices. 'The Witches' Lair' is also great as it dives into the lairs of the witches, revealing more about their nature and how they are connected to the magical girls. Additionally, 'Kyubey's True Intentions' is an interesting one as it tries to uncover the real motives behind Kyubey's actions, which adds a whole new layer of depth to the original story.
One interesting plot twist could be that one of them is secretly working for an enemy all along. For example, Sayaka might be unknowingly influenced by a new witch to turn against Kyoko. Another is that they discover a hidden power within their bond that changes the whole dynamic of the story. Maybe it's a power that can rewrite the rules of the Madoka Magica world.
One common theme is the exploration of different power systems. For example, when crossing over with other magical girl shows, how the magic in Madoka Magica compares and interacts with the other's magic system. Another theme is the clash of different worldviews. Characters from Madoka Magica, who often face a rather bleak reality, meet characters from more optimistic universes, and this creates a lot of interesting conflict and growth opportunities.