One idea could be a crossover with another popular anime like Naruto. For example, Jotaro could meet Naruto and they could have a battle of wills and powers. Naruto's positive attitude might clash with Jotaro's more stoic nature.
Well, it could be about the JoJo characters getting transported into the Warframe universe. They might team up with the Tenno to fight against common enemies like the Infested. For example, Jotaro could use Star Platinum's power along with a Warframe's abilities to take on hordes of foes.
One idea could be that Kira Yoshikage from JJBA somehow ends up in the Naruto world. Maybe his Stand ability could be misinterpreted as some kind of strange ninja jutsu. He might try to live his quiet life there, but his actions would surely draw the attention of the ninja. For example, if he starts using his Stand to kill people in the ninja villages, it would be like a new and unknown threat to the ninja, and they would have to figure out how to deal with it.
Well, you could focus on the character crossovers. Imagine Jotaro Kujo meeting Ichigo Kurosaki. Jotaro's cool and collected demeanor would contrast with Ichigo's more hot - headed nature. They could learn from each other's fighting styles. And then there's the possibility of Stand users having to adapt to the spiritual energy in the Bleach world and vice versa. This could lead to some really interesting power - up and training sequences for the characters involved.
After that, start writing the introduction. You can introduce the JJBA characters in their normal setting first, and then gradually introduce the elements of the other universe. This helps the reader get grounded in the story before things get really crazy. Also, don't be afraid to add your own unique twists to the story to make it stand out.
First, you should do your research on both JJBA and Bleach. Know the characters, their powers, and the rules of their respective universes. Then, come up with a basic plot idea, like a conflict that involves both universes. For example, a villain who wants to merge the two worlds for his own evil purposes. After that, start thinking about which characters you want to feature and how they will interact.
First, decide on the starting point. If you start in the JJBA world with Kira Yoshikage, you could have him accidentally open a portal to the Naruto world. His confusion and his instinct to keep his murderous habits hidden would drive the initial plot. He might try to blend in, but his different appearance and behavior would make it difficult. In the Naruto world, he could encounter Naruto and his friends who would sense something is off about him.
Kakyoin and Loki Warframe would make a fascinating pair. Kakyoin is very intelligent and strategic with his Hierophant Green stand. Loki, on the other hand, is all about stealth and deception. They could combine their skills to infiltrate enemy bases in the crossover. Kakyoin could use Hierophant Green to scout ahead while Loki keeps them hidden from detection.
A crossover with One Piece might also work well. Joseph Joestar could find himself on the Grand Line, interacting with the Straw Hat Pirates. His hamon abilities could be a strange and new power for the pirates to encounter, and he could help them out in battles against the likes of the World Government or other powerful foes, while also learning about the Devil Fruits and Haki.
One popular SCP JJBA crossover fanfiction is 'SCP - JoJo's Bizarre Adventure: The Stand Users'. It combines the unique and often dark elements of the SCP universe with the flamboyant and power - based world of JJBA. The story weaves together the two in a way that keeps readers on their toes, as characters from both universes interact in unexpected ways.