One main theme is sacrifice. Itachi sacrificed his own reputation and relationship with his family and clan for the greater good of the village. Another theme is loyalty, as he was loyal to the Hidden Leaf even though his clan was planning a coup. And there's also the theme of redemption, as he tried to make up for his actions in his own way.
Sure. 'Itachi Uchiha: Dark Night's Tale' is a great one. It delves deep into Itachi's backstory, his complex relationship with Sasuke and his motives for his actions. Another interesting one could be 'Itachi's Path: The Uchiha Prodigy' which focuses on his growth as a ninja and his inner struggles within the Uchiha clan.
In Itachi yaoi fanfiction, Itachi is often depicted as a complex and mysterious character. He is usually highly intelligent and powerful, which makes him an alluring figure in romantic or relationship - based stories. His loyalty, whether it be to his family, his village, or his love interest in the yaoi context, is also a common characteristic explored.
Wonder Woman is another character that might be paired with Itachi. Her Amazonian warrior heritage and Itachi's shinobi skills can be compared and contrasted. Their different views on justice, with Wonder Woman coming from a more idealistic place and Itachi having a more pragmatic approach, can lead to some great character - driven storylines in fanfiction.
His character could be developed by showing his adjustment to the Fairy Tail world. He could start off as a loner, but gradually open up to the members. His backstory as a ninja could be explored further in relation to the new environment, like how his past actions affect his new relationships.
Naruto would adapt to Itachi's life in several ways. Socially, he'd have to get used to Itachi's connections and rivalries. For instance, his relationship with Kisame would be different as Naruto. He might try to influence Kisame in a more positive way. Emotionally, he'd have to deal with Itachi's internal struggles. Itachi had a lot of guilt and secrets, and Naruto would have to either come to terms with them or find a way to resolve them. And in terms of combat, he'd practice Itachi's signature moves over and over to make sure he could use them effectively in battle.
They could develop a mentor - mentee relationship. Itachi uses his knowledge of the Sharingan to teach Naruto new combat techniques. As they train together, they bond over their shared experiences of loss and their desire to protect the people they care about. Naruto might also help Itachi come to terms with his past actions and find some peace within himself.