In a Naruto 4th Shinobi War fanfiction, we could have a plot where the Akatsuki actually had a hidden agenda that was not related to the tailed beasts at all. They could be using the chaos of the war as a distraction to perform some other dark ritual. And perhaps a young shinobi discovers this and has to race against time to stop them while also fighting in the war.
One idea could be exploring the backstories of minor characters during the war. For example, how a random shinobi from a small village coped with the chaos. Another could be a what - if scenario, like what if a certain alliance was formed differently. Maybe a group of rogue ninjas decided to side with one of the major villages instead of staying neutral.
A third idea is a story centered around a shinobi who was thought to be dead but actually survived and is now trying to get back to the battlefield. Along the way, they discover secrets about the origin of the war or new jutsu that could turn the tide of the battle. They have to overcome their own physical and mental weaknesses while also evading the enemy who believes them to be dead.
One idea could be focusing on a minor character's perspective during the war. For example, a young genin who is caught in the middle of the chaos. They could witness the great battles between the powerful shinobi and have their own journey of survival and growth.
One idea could be focusing on a young, unknown shinobi who rises to prominence during the war. They might have a unique jutsu that catches everyone's attention.
One idea could be focusing on a young and inexperienced ninja who gets thrust into the chaos of the Third Shinobi War and has to quickly learn to survive. Maybe they form an unlikely alliance with a ninja from an enemy village because they both realize the senselessness of the war at a personal level.
One idea could be exploring the backstories of minor characters during the war. For example, how the normal shinobi were feeling and what they were doing on the sidelines. Another could be a what - if scenario where a different alliance was formed among the shinobi villages.
One idea could be exploring the backstories of minor characters during the Fourth War. For example, how the ordinary shinobi coped with the chaos and fear. Another could be a different strategy for the Allied Shinobi Forces that changes the course of the war in unexpected ways.
One idea could be focusing on a young shinobi who is an unknown hero during the war. They might use some unique and forgotten jutsu to turn the tide in crucial battles.
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.
One idea could be to focus on a young and inexperienced ninja who gets caught in the middle of a major battle during the Third Shinobi War. They could witness the horrors of war and have to quickly learn to survive. Maybe they form an unlikely alliance with a ninja from the enemy side who also has a different view on the war.