Goku Black's super strength could be relative to the Grimm in RWBY. Since the Grimm are often very strong and durable, Goku Black's strength might need to be adjusted slightly so that he doesn't completely overpower them all at once. His strength could be on a level where he can take on multiple high - level Grimm at the same time, but still face challenges from the strongest ones.
His ability to teleport could be more in line with the semblances in RWBY. Maybe it would be limited by the same rules as some of the characters' semblances, such as having a cooldown period or being affected by certain environmental factors. This would make his battles in the RWBY universe more balanced and interesting, as he couldn't just teleport freely all the time.
His speed would increase. Goku Black is very fast, and his training could make Naruto move at blistering speeds. Also, Naruto's power attacks would be stronger. Goku Black's training methods would push Naruto to new limits.
Naruto would gain a new perspective on combat. Goku is a martial artist at heart. Naruto, being raised by him, would develop a more refined combat style. He would not rely solely on his shadow clones or Rasengan. Instead, he would incorporate more hand - to - hand combat skills. His ability to adapt in battle would also improve. He would be able to analyze his opponents' moves quickly and come up with counter - strategies based on his new combat knowledge, which is a mix of ninja skills and Goku - like martial arts.
His chakra abilities might be affected by the presence of Dust in RWBY's world. Maybe he could combine Dust with his jutsu. For example, using fire - type Dust to make his Fireball Jutsu even hotter. His physical abilities like speed and strength would still be an advantage, but he'd have to learn to use them in the context of fighting Grimm and other RWBY threats.
In the past, Team RWBY's abilities could change in various ways. Ruby's semblance of speed would give her an edge in battles, but she might also attract unwanted attention as people in the past may not be used to such swift movements. Weiss's Glyphs could potentially be more powerful in the past if the Dust in that era has different properties. Blake's ability to create clones could be misinterpreted as some kind of dark magic, causing her to have to be more careful about using it. Yang's power might be more difficult to control as the technology to understand and manage it might not exist, making her a bit of a loose cannon in the past.
His ki - based attacks would be a new and powerful addition. In High School DxD, most of the powers are related to magic, sacred gears, and demonic or angelic powers. Goku Black's ki blasts would be a completely different form of energy that could catch everyone off - guard.
He would add more chaos. Since he's a powerful and unpredictable character, his actions would disrupt the normal flow of the tournament. He might target strong fighters first to gain an advantage.
Ruby's speed might increase even more due to the sense of danger from the Friday the 13th elements. She could be constantly on high alert and her scythe attacks could be more erratic and fast - paced.
Naruto's ability to use chakra could give Goku a new way to power up. Maybe Goku could learn to combine chakra with his ki, creating a whole new level of power. Also, Naruto's shadow clone jutsu could be used by Goku in his training, allowing him to fight multiple opponents at once and improve his skills faster.
Goku Black could also be a part of some sort of experiment gone wrong in the RWBY world. Maybe some scientist was trying to combine different types of energy and accidentally brought Goku Black into their realm. This would lead to a lot of chaos as he starts causing trouble and the RWBY teams have to stop him.
The story could start with Goku being pushed to his limits by Goku Black's attacks. But then, he remembers his training with the Kai's and how they taught him to focus his energy in a more efficient way. He then uses this knowledge to create a more powerful Kamehameha that breaks through Goku Black's defenses and kills him.