One interesting story could be about Naruto joining the Alvarez Empire and having to adapt to their different culture and ways of doing things. Maybe he has to prove himself in their combat trials.
One idea could be exploring the backstories of the Alvarez Empire soldiers. Maybe there's a young soldier who has doubts about the empire's motives and ends up befriending a Fairy Tail member. This could lead to a story of self - discovery and changing loyalties.
Obviously, Naruto is one of the main characters. In the context of this fanfiction, he is the one who gets involved with the Alvarez Empire.
One idea could be exploring the backstories of the members in the Alvarez Empire. For example, showing how they joined the empire and what their motives were.
One possible plotline could be that Naruto is somehow corrupted or misled. Maybe he discovers some dark secrets within Konoha that he believes can only be resolved by its destruction. As for the Alvarez Empire, they might see an opportunity to expand their influence in the chaos Naruto creates and form an uneasy alliance with him at first.
One popular Naruto Alvarez fanfiction might be those that explore new jutsu for Naruto. For example, a story could have Naruto develop a unique space - time jutsu under the guidance of Alvarez. Another type could be about Naruto and Alvarez teaming up to face a new, powerful enemy that neither could defeat alone. And there could also be fanfictions that focus on their friendship and how they influence each other's growth.
One interesting concept could be the unique blend of Naruto's ninja world with the elements of the Lyon Empire. For example, how the ninja skills might interact with the political and cultural aspects of the empire. Maybe ninjas could be used as special agents within the empire's power structure.
Character interactions are a big draw. Picture Naruto himself interacting with an emperor or empress from the other empire. Their different values and goals would surely lead to some intense and thought - provoking dialogues, and perhaps even a change in Naruto's view of leadership.
One interesting plotline could be the exploration of new jutsu within the context of the Eternal Empire. Maybe characters develop unique powers that are a blend of traditional Naruto abilities and new, empire - related powers.
One interesting plot could be the exploration of a darker side of the Naruto universe where the main characters face moral dilemmas they never had to in the original series. For example, Naruto might have to make tough choices between saving his friends and sacrificing his own principles in the 'dark empire' setting.
Zeref, of course. He is a central figure in the Alvarez Empire. His power and his role as the emperor or leader make him a crucial character to include.