Well, a cool plot could be that the banished mercenary was actually framed for a crime he didn't commit. So, he comes back to prove his innocence and in the process, uncovers a conspiracy within the ninja villages. Maybe he teams up with some of the outcast ninja who also believe in his cause. He could also have a special item or power that the villains are after, which adds more drama to the story.
A possible plot for a Naruto Banished Mercenary Fanfic could involve the mercenary being banished because he refused to follow an unethical order. After being banished, he becomes a sort of vigilante, helping those in need outside the traditional ninja system. When he returns to the Naruto world, he challenges the existing power structures and tries to reform the way ninja operate. He might also have a love interest from his past who is now in a difficult situation within the village, which further complicates his return.
One idea could be that the banished mercenary has unique jutsu skills learned from different lands during his mercenary days. He could return to the Naruto world with a new perspective and hidden motives, perhaps trying to unite different ninja clans against a new, greater threat. Another plot idea is that he has a connection to an ancient prophecy that was thought to be forgotten, and his banishment was actually part of a grand scheme to protect him until the time was right.
A possible plot could involve the banished mercenary being from a long - lost clan. The reason for his banishment was a false accusation by a rival clan. As he wanders the Naruto world as a mercenary, he discovers clues about his clan's true heritage and power. He then uses his skills as a mercenary to gather allies and resources to prove his clan's innocence and restore its honor. Along the way, he crosses paths with Naruto and his friends and they either help or hinder his quest depending on the situation.
For the banished mercenary, his character development can be made interesting by exploring his backstory. If he was banished because of a misunderstanding, gradually revealing the truth behind it can be a great way to develop his character. He might initially be a lone wolf, but as he gets involved in various adventures, he realizes the importance of having comrades. His views on the shinobi way could change over time. For instance, he might start off believing that only power matters but then, after seeing the selfless acts of others, he begins to understand the value of things like loyalty and friendship. This transformation from a jaded mercenary to someone with a more positive outlook on the shinobi world would be very engaging.
In some 'naruto is banished fanfic', one interesting plot could be Naruto finding a new hidden village that accepts him wholeheartedly. He might then train with unique jutsus there and form new alliances.
One idea could be that Naruto is banished due to a false accusation against him that endangers the village's secrets. His wife, say Hinata, decides to go with him. They start a new life in a small, remote village, and Naruto uses his skills to protect the new place from various threats, gradually earning the respect of the locals.
One plot idea could be that Naruto, after being banished, crosses paths with Kurenai who is on a solo mission. She initially has her doubts about him due to his banishment but gradually realizes he was wrongly accused. They team up to face a common enemy that threatens the village from afar. This could lead to a growing bond between them.
One interesting plot could be that Naruto is betrayed by the Hidden Leaf Village due to false accusations of being a spy for a powerful enemy. Banished, he then discovers new powers or allies outside the village. He might form his own group of outcasts and come back to the village to prove his innocence and seek revenge on those who wronged him.
Well, one interesting plot point could be how Naruto copes with being banished in the first place. Maybe he discovers new powers or allies during his time away. Another could be his grand return and how the village reacts to him, whether they welcome him back with open arms or are still skeptical.
It could be an original character. For example, a ninja who was born into a minor clan but had great potential. However, due to political intrigue and jealousy from a major clan, he was framed and banished. He then became a mercenary to survive. Another option could be a character who was once a part of a secret ninja organization and was banished when he disagreed with their methods. Now, as a mercenary, he returns to the Naruto world with a vendetta against those who wronged him.
Perhaps there's a political conspiracy in the village. Naruto and Shikamaru discover some dark secrets that certain powerful people in the village don't want exposed. So, they are banished to keep them quiet. They then form an alliance with other outcasts and work towards uncovering the truth and returning to the village to set things right. This could involve a lot of action scenes as they fight off those sent to stop them.
In this fanfiction, Naruto and Kakashi are banished because of a prophecy that some in the village misinterpret. The prophecy seems to suggest they will bring doom, but in reality, it's about a different kind of change. While banished, they explore different lands, learn new jutsu from other ninja clans, and eventually return to the village stronger and wiser, proving the prophecy was misread.