In a 'Darth Vader No Suit Fanfiction', a possible plot is that Darth Vader, without his suit, is stranded on a strange planet. He has to survive without the technological enhancements the suit provided. As he struggles, he meets a local tribe. At first, they are afraid of him, but gradually they start to trust him. Through this experience, he begins to see life from a different perspective. He might also start to regain some of his old physical abilities through natural means on the planet, and this newfound strength could be a turning point in his character development, making him consider a different path than the one of the Sith.
One idea could be exploring Darth Vader's identity before he became encased in the suit. Maybe he rediscovers his old self and tries to reconnect with his past relationships. Another could be him having to face the Jedi without the intimidating suit, relying solely on his raw Force abilities.
Perhaps Darth Vader's dark side powers are misinterpreted in the Naruto world as a new and extremely dangerous form of jutsu. Naruto and his friends might try to find a way to seal these powers. Meanwhile, Vader is on a quest to find a way back to his own universe, and in the process, he starts to question his own dark ways after seeing the camaraderie among the Naruto characters. He could end up having a change of heart and use his powers for good in the Naruto universe.
One idea could be a story where Darth Vader discovers Leia's true identity earlier and struggles with his loyalty to the Empire and his newfound knowledge of his daughter. He could secretly protect her from the Emperor's wrath.
In some fanfictions, Darth Vader's upgraded suit might have enhanced weaponry. For example, it could have built - in lasers that are more powerful than the standard ones. This would make him even more formidable in combat.
Another plot could be set in an alternate universe where Ahsoka manages to reach out to the little bit of Anakin still left in Darth Vader. She tries to redeem him, and through a series of encounters, they start to question their own paths and the Sith vs. Jedi ideology.
One idea could be that the OC is a rebel spy who gets captured by Darth Vader. Instead of killing her immediately, he becomes intrigued by her tenacity and they start to have a series of tense conversations that gradually lead to an unexpected understanding between them.
One idea could be a story where Darth Vader secretly trains Luke in the ways of the Force before Luke fully realizes who he is. This would add an interesting layer of secrecy and moral conflict for Vader.
One idea could be a story where Luke discovers a way to temporarily reverse Vader's Sith corruption, leading to some heart - to - heart conversations between them as Anakin. Another could be a fanfic where they have to team up against a new, greater threat in the galaxy that neither the Rebels nor the Empire can handle alone. Maybe a story where Luke gets trapped in a Sith - created alternate dimension and Vader has to go in and rescue him to atone for his sins.
One idea could be that Darth Vader discovers his connection to Leia earlier and secretly tries to protect her from the Emperor's more sinister plans. He might use his position within the Empire to subtly divert threats away from her.
One idea could be a crossover with Star Trek. Darth Vader could find himself on the Enterprise and have to deal with the Federation's values, which are very different from the Sith's. Maybe he'd be forced to team up with Kirk and Spock to fight a common enemy.
One plot idea could be a time - travel scenario where Ahsoka is sent back in time and has to face Darth Vader before he fully became the Sith Lord she knew. She could try to prevent his fall. Another idea is a story set in an alternate universe where Ahsoka and Vader team up against a greater threat, forcing them to put aside their differences. Maybe a plot where Ahsoka is captured by Vader and he has an internal struggle about what to do with her, given their past relationship.