Well, it can add depth to your understanding of Shikamaru and Sasuke's characters and their development. However, if you're short on time or not overly interested in their specific arcs, you could skip it without missing out on the core story.
One idea could be that they go on a special mission to a hidden village. Naruto's enthusiasm, Sasuke's power and Shikamaru's intelligence combine to solve the mystery of the village's strange disappearances. They face many challenges along the way, like tricky traps and powerful enemies. Naruto uses his Rasengan, Sasuke his Chidori, and Shikamaru his shadow jutsu to fight their way through.
I think young Sasuke would have a very intense reaction. He was so consumed by his hatred for Itachi at that young age. A Sasuke vs Itachi fanfiction would be like a trigger for him. He would be eager to see how the fictional fight is portrayed. If Sasuke in the fanfiction is shown as strong, it might fuel his own ego and make him strive even harder to become powerful. However, if the fanfiction shows Itachi as superior, it could enrage him. He might feel that it undermines his own goal of defeating Itachi and he might even want to find the writer to correct their 'wrong' view.
I like Naruto in these fanfics because he always stays true to his beliefs. He is constantly trying to bring Sasuke back to the village and is willing to fight for their friendship.
One of the best moments is when they have a rematch that showcases their growth. Naruto has become stronger with his new jutsu, and Sasuke has further mastered his Sharingan powers. The intense battle of ideologies during the fight is captivating.
Well, it could be Orochimaru. Even if they travel in time, Orochimaru's thirst for power and knowledge might make him an antagonist. He could see Sasuke and Shikamaru as threats to his plans, especially if they are trying to change the past which might interfere with his own schemes.
One great Naruto, Sasuke, and Shikamaru time travel fanfiction is 'A New Beginning'. It has an interesting plot where they travel back to change key events in the ninja world. The character development is on point, and it really delves into how their knowledge of the future affects their actions in the past.
One interesting plot could be that they travel back to the time when the Uchiha clan was about to be massacred. Sasuke might try to change the fate of his clan, while Shikamaru uses his intelligence to strategize and deal with the political implications. They could face many challenges, like not being believed by the people of that time or accidentally causing more chaos.
They could go on an adventure to find a rare and powerful jutsu. Naruto would be eager to learn it, Sasuke would see it as a way to increase his power, and Shikamaru would be dragged along reluctantly at first. But during the search, they discover that the jutsu has a dark side that they must decide whether to use or destroy.
It really depends on the writer's preference. Some fanfictions might have Naruto winning because of his unwavering belief in friendship and his ability to draw on the power of the nine - tails. Others might have Sasuke winning due to his strategic mind and mastery of the sharingan.