One interesting plot idea could be Kakashi traveling back in time to before the Uchiha massacre. He could try to prevent it, which would completely change the future of the Naruto world. Maybe he'd have to face off against Danzo and his schemes early on.
Another plot could involve Kakashi traveling to the time of the First Hokage. He could learn new jutsu directly from Hashirama and bring that knowledge back to his own time. This might also give him insights into how to better handle the tailed beasts in his era.
One plot idea could be that fem Naruto and Kakashi travel back to the founding of Konoha. They could use their modern - day knowledge and skills to influence the early development of the village in positive ways, like introducing new training methods. Another idea is that they travel to a time when a great enemy first emerged and they work to stop the threat before it becomes too powerful.
A cool plot would be Kakashi traveling back to a time during one of the great ninja wars, say the Third Great Ninja War. He could use his knowledge of future jutsu and strategies to turn the tides of battles that were previously lost. He might also be able to save comrades who died in the original timeline, and in the process, change the future of many ninja families.
Well, a cool plot might be Kakashi time - traveling to the era of the First Hokage. There, he could learn ancient jutsu and bring them back to his time. Maybe he gets involved in a conflict that was long forgotten but has implications for his present. He could also time travel during a crucial battle in his own past, like the fight against Obito, and change the outcome in unexpected ways.
Well, in some 'kakashi time travel fanfiction', Kakashi might travel back to change the fate of his village. He could go back to a time when there were internal conflicts in Konoha and resolve them before they escalated. Also, he could have the chance to reunite with his loved ones who had passed away, like his father. This would add a whole new layer of emotional depth to the story.
Perhaps a really cool plot twist is that the time travel was actually a trap set by an old enemy. When Kakashi and Naruto travel back, they find out that this enemy has been manipulating events from the past all along. They then have to not only fix the past but also figure out a way to stop this enemy from using the past to destroy their future.
They could time - travel during a great war in the past. Kakashi and Sakura might find themselves in the middle of battles they only read about in history books. They could use their modern - day skills to change the outcome of certain battles. This would also have a huge impact on the present - day Naruto world as they know it.
One idea could be that Sakura, as an Anbu, travels back in time and tries to prevent certain tragedies in Kakashi's past. Maybe she stops Obito from 'dying' initially, which would change the entire Naruto storyline in a major way.
Maybe they time travel to a point where a major battle was lost in the past. Kakashi and Team 7 could change the outcome of that battle. For example, if they go back to the battle against the Nine - Tailed Fox when it first attacked Konoha. They might be able to prevent some of the destruction and save more lives. Or they could travel to a time when a powerful ninja was wrongly exiled, and they work to clear that ninja's name and change the course of history.
One idea could be that Obito and Kakashi are sent back to their childhood days. Obito then tries to prevent certain tragedies that happened in their past, like the death of his comrades. He might also try to change Kakashi's cold - hearted nature that developed over time. This could lead to a whole new set of relationships and events in the Naruto world.
A possible plot is that Naruto discovers a hidden power within Kakashi that even Kakashi was unaware of. This discovery leads them on a journey to explore the origin of this power. Maybe it's related to an ancient clan. As they dig deeper, their relationship grows stronger and they face many challenges together from enemies who also want this power.