In a crossover with Sailor Moon, Sailor Venus could be part of the harem. She is a strong fighter like Goku in her own way, and their different powers and personalities could create interesting dynamics.
One possible interesting plot could be Goku, in his godlike form, being transported to different universes where he meets various female characters from different shows or stories. He then has to form alliances with them to fight a common evil. As they spend time together, romantic feelings start to develop among them, creating a harem dynamic.
One idea could be Goku from Dragon Ball crossing over into a world like Fairy Tail and having a harem of the female mages there. Maybe he helps them in battles and gradually forms relationships with them.
Bulma could be one. She already has a long - standing relationship with Goku in the original series. Her intelligence and sass could add an interesting dynamic to the harem. Another could be Android 18. She's strong and independent, and her interactions with Goku could be really cool in a harem scenario.
One idea could be that Goku is transported to a different universe where he meets various female characters from different anime. They are all intrigued by his power and his pure-hearted nature, and a harem dynamic starts to form as they all want to be around him and train with him.
Bulma could be one. She already has a long - standing relationship with Goku in the original series. Another could be Sailor Moon. Her strong sense of justice and powerful abilities would make for an interesting addition. Also, Mikasa from Attack on Titan with her combat skills and loyalty could be part of the harem.
One common theme is the exploration of Goku's relationships outside of his usual fighting and training. Another is the development of the female characters in the harem, showing their unique personalities and how they interact with Goku.
It can be. There are fans who love to explore different relationship dynamics for Goku in a harem - like setting in fanfiction. But the 'lemon' part might put off some readers. Some communities have strict rules against such content. So in a more open - minded and lenient fanfiction community, it could be relatively popular, but not so much in a conservative one.
Bulma could be one of the characters in the harem. She has a long - standing relationship with Goku and her intelligence could complement Goku's power. Another could be Chi - Chi, his wife. Her fierce loyalty and determination would make her an interesting part of the harem.
Love and redemption can also be common themes. Sometimes the harem members help Goku Black to find a new path or redeem himself through their love. It adds an interesting layer to his character.