Well, perhaps Naruto could find himself in the middle of a crucial battle during the Second Shinobi War. He could befriend some of the young shinobi who later become important figures. He might help them out in a difficult situation, like rescuing a group of shinobi from an ambush. This would change the course of the war in small ways and also form strong bonds with those from the past.
He could meet the young Hiruzen Sarutobi. Naruto might learn a lot from him about the history and politics of the shinobi world at that time. They could also exchange jutsu knowledge to some extent.
It could be an original character. For example, a young ninja from a small, unassuming clan that has been overlooked in the grand scheme of the war. But as the war progresses, they show extraordinary skills and courage, becoming a key figure in the battles.
Well, the plot could revolve around a shinobi who has a special ability that is both a curse and a gift. During the Second Shinobi War, this shinobi is hunted by different factions because they believe his ability can be used to tip the scales of the war. However, the shinobi doesn't want to be a part of the war and is constantly on the run. In the end, he might be forced to use his ability to save a large number of people, including those from the villages that were hunting him, and in doing so, he changes the perception of his ability.
A civilian who somehow gets involved in the war and discovers they have latent shinobi abilities. They could start as a clumsy and inexperienced character but grow into a powerful force.
'The Unseen Hero of the 4th War' is a great one. It focuses on a character who is often overlooked in the original story but plays a crucial role in the fanfiction. The writing style is engaging and it really dives deep into the character's emotions during the chaos of the war.
One possible plot twist could be Naruto changing the outcome of a major battle. For example, in the Second Shinobi War, there were many crucial battles. Naruto might use his future knowledge to prevent the death of a key ninja. This would have a huge impact on the future of the ninja world as that ninja could then go on to change other events.
If Naruto was born before the Second Shinobi War, the story would be drastically different. For one, the political landscape of the ninja world at that time was very different. There were different power struggles and alliances. Naruto might have grown up in a more chaotic and war - torn environment. His presence could have potentially changed the outcome of some of the battles during the Second Shinobi War. Maybe he could have influenced some of the key players in a way that would lead to a different future for the ninja villages.
In a fanfiction where Naruto is born during the Second Shinobi War, he could potentially be a major asset to the Leaf Village much earlier. Since he's the jinchuriki of the Nine - Tails, his power could be harnessed for the war effort. However, this also means he'd be in more danger from enemy villages who would want to either capture or kill him. His relationship with the villagers might be different too. Instead of being shunned for the Nine - Tails inside him, they might see him as a necessary evil for the village's survival.