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.
Kakashi's abilities would likely be enhanced in the past. He has all the knowledge and skills he's gained in the future. So, his combat skills would be more refined. His Sharingan would be even more powerful as he would know better how to use it. He might also be able to teach his younger self some new jutsu that he learned over the years.
When the Konoha 12 time - travel to the past, their abilities would change significantly. Take Rock Lee for example. In the past, there might be different training methods that could further boost his physical strength and taijutsu skills. He could learn from the masters of old and bring back new techniques. For Ino, her mind - transfer jutsu might work differently in the past due to the different mental states and chakra signatures of the people then. And for Shikamaru, his strategic thinking would have to adapt to the different political and combat situations of the past. Their abilities would not only change in terms of power but also in how they are applied in the context of the past's ninja world.
Well, a plot might involve Team RWBY traveling back to the time when the first Huntsmen and Huntresses were being trained. They could get involved in the early development of combat techniques and weaponry. Maybe they end up influencing the way things are taught, for instance, introducing some of their more modern strategies. Or perhaps they go back to a time when a powerful relic was first discovered and have to protect it from falling into the wrong hands, which could change the entire future of Remnant.
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.
They might become closer as they realize how important they are to each other in the future.
Orochimaru's experiments and his knowledge of forbidden jutsu would be far ahead of the time he travels back to. He could use this to his advantage, perhaps by creating new techniques based on the limited knowledge of the past. However, he also has to be careful not to change the future too much as his actions in the past could have unforeseen consequences for his future self.
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.
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.
Yang and Blake's relationship could be affected in a positive way. Yang might make jokes about the fanfiction that Blake finds funny, strengthening their bond. Weiss could become more open to different types of stories, which would change her interactions with the team. Ruby would be the driving force in getting everyone involved in the discussion about the MLP fanfiction, making the team more united in their shared interest.
Ruby would probably be very excited. She loves new stories and ideas, so fanfics would be like a treasure trove for her. Weiss might be a bit more reserved at first, but would gradually get into it if the fanfic was well - written. Blake would be looking for deeper meanings and connections in the fanfics, while Yang would be the one to cheer and comment loudly on the action - packed or humorous parts.