One idea could be exploring the backstories of minor characters during the war. For example, how the war affected the normal villagers who were not shinobi. Another could be a story where a new, unexpected alliance forms between different ninja clans to fight a common, greater threat that was overlooked during the original war.
In a fanfiction scenario where Naruto starts the 4th Shinobi War, it would completely change the whole Naruto universe's narrative. Naruto is known for his desire for peace, so if he starts the war, it might be due to some extreme manipulation or a misunderstanding of the situation. For example, he could be tricked by an enemy who has disguised themselves as an ally and convinced Naruto that starting the war is the only way to protect the Leaf Village. This would lead to a situation where all his friends and comrades would be forced to either oppose him or be dragged into a war they didn't want.
In some fanfictions, if Naruto was sent to the Third Shinobi War, he could change the course of many battles. His unique jutsus like the Rasengan might surprise the enemies. He could also inspire his comrades with his never - give - up attitude.
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.
I think Obito could be really interesting. His complex backstory and his role in the war were so crucial. You could explore his internal struggle further, like his lingering feelings for Rin and how that influenced his actions during the war in more depth.
The fanfic could also focus on the personal lives of the characters. Naruto might finally have time to focus on his relationship with Hinata. There could be stories about how they build their family, and how Naruto balances his role as a family man with his duties as a hero of the ninja world. At the same time, other characters like Sasuke could also be exploring their new identities in a post - war world, trying to find their place and purpose.
There could be some original characters as main characters too. For instance, a young shinobi from a small, unknown village who rises to prominence during the Third Shinobi War. This character could bring a fresh perspective and unique abilities to the story, interacting with the well - known Naruto characters and changing the course of the war in the fanfic.
In a fanfiction about Naruto, the Gura Gura Fruit, and the Third Shinobi War, perhaps the Gura Gura Fruit is a new, mysterious element introduced into the war. Naruto, being the curious and adventurous ninja he is, might be the first to discover it. His friends and allies could be initially wary of this strange power, but as Naruto learns to control it, they see its potential in turning the tide of the war against powerful enemies such as Orochimaru or the Hidden Stone Village's forces.
In a 'godlike Naruto' Fourth Shinobi War fanfiction, Naruto could have a connection to a divine entity. Maybe he discovers he is a descendant of a god of the ninja world. This newfound heritage gives him superhuman strength, speed, and the power to foresee his opponents' moves. He uses these powers to single - handedly take on Madara Uchiha and Kaguya. His godlike status also earns him the respect and loyalty of all the shinobi clans, uniting them under his leadership against the common enemy.
Obviously, Naruto would be one of the main characters. He's the central figure in the Naruto series, especially when it comes to his early days as a shinobi. His friends like Sasuke and Sakura would also likely be main characters as they were always by his side during his initial shinobi experiences.