What would have happened if Luke joined Vader in fan fiction?

It could lead to a whole new power struggle within the Empire. Maybe Vader would try to reform it or take it over completely.

The relationship could develop in a complex way. Since Vader has captured Luke, there's a power imbalance. However, as they interact, Luke might try to reach out to the good in Vader. Vader, in turn, might be conflicted. He could start to protect Luke from the Emperor's harsher plans, leading to a strange alliance within the captivity.

If Obi-Wan joined Dooku, there might have been a power struggle between them. Also, it could have affected the relationships with other characters and the balance of the Force in unexpected ways.

It could have led to a deeper development of their relationship and more adventures together. Maybe they would have faced tougher challenges and grown even closer as a team.

It could lead to a major power shift and chaos in the wizarding world. Dumbledore's alliance with Grindelwald would likely cause a lot of upheaval and maybe even change the course of the story completely.

It could lead to a lot of interesting conflicts and character developments. Scourge's dark past and aggressive nature might clash with ThunderClan's values and cause internal tensions.

It could lead to all sorts of interesting plot twists. Maybe Luke would have a change of heart and become a loyal Imperial, or maybe he'd be a spy for the Rebel Alliance.

It could have led to a completely different story arc. Maybe there would have been less internal conflict within the clan and Bluestar's leadership might have taken a different direction.

Well, it could have led to a whole new dynamic in their relationship and maybe changed the course of the story significantly.

Well, if Edward didn't leave, there could have been more opportunities for character growth and exploration of their connection. Maybe they would have faced new challenges together instead of separately.