Definitely Orihime. She is the type who would be easily attracted to Goku's pure - heartedness and his determination to protect. Her own insecurities might be soothed by Goku's confidence. Rukia, with her sense of duty, could find herself drawn to Goku's selfless acts of heroism. And Neliel could also be part of the harem. Her child - like form and yet powerful true form would create an interesting relationship with Goku, as he might be protective of her in her child form and respect her power in her true form.
Honestly, comparing the strength of anime Goku and manga Goku is tricky. Both versions have their unique strengths and challenges depicted differently, making it hard to make a clear-cut comparison.
Well, Vegeta would be a likely character. He might be initially suspicious of the female Goku. Maybe he thinks she's a threat or just can't believe there's another Goku - like being. He could be there to add some comical moments as he tries to understand the situation.
The plot could revolve around Goku teaching Caulifla and Kale some of his unique techniques. Caulifla is eager to learn and Kale follows her lead. As they train together, they form a strong bond. Eventually, they face a threat to the entire multiverse and their combined powers are the key to saving it. This way, it focuses on their growth as characters and their friendship.
In general, it's a bit of a toss-up. The strength of Manga Goku and Anime Goku can vary depending on the specific arcs and battles. Sometimes, it might seem like one is stronger in a particular situation, but that could change in another.
Another possible main character could be the villain that forces the two Gokus to meet. This villain could be a new, super - powerful threat that the two Gokus need to deal with. Their meeting becomes a crucial part of the story to defeat this powerful foe.
One of the characters who could betray Goku is Piccolo. Although they've been allies for a long time, in fanfiction, things can change. Perhaps an ancient evil force takes control of Piccolo's mind and makes him turn on Goku. Or it could be Krillin. He might be influenced by an outside force that convinces him Goku is becoming too dangerous. Also, don't forget about the Kais. If there's some sort of power imbalance or a threat they perceive from Goku, they might betray him to maintain the order of the universe in the fanfiction.
Well, it could be about Goku Jr learning some of Goku's most powerful moves. Maybe Goku teaches him the Kamehameha. They might also go on an adventure together, like fighting a new and powerful enemy that neither could face alone.