He would grow in terms of self - discovery. Being barred from the ninja path, he'd have to search for a new identity. This could lead him to explore his own values more deeply. He might find that there are other ways to be a hero, like helping the poor or taking care of the environment, and his character would evolve to embrace these new roles.
He'd become more adaptable. Stuck in this new world, he has to quickly adjust to the differences. This would make him better at handling unexpected situations in the future.
Naruto's chakra control and combat skills would develop differently. Hanzo was a master of his own unique techniques. Naruto would be trained in those, and perhaps develop his own spin on them. His fighting style might be more stealth - based and less reliant on brute force like his Rasengan - centric style in the original. He would also have a different sense of honor, influenced by Hanzo's code of conduct.
His character could become more complex. He'd have to balance his own values from Konoha with the new ones in the Covenant. This internal struggle would likely make him more mature. For example, he might question his previous beliefs about power and leadership.
His understanding of pain and suffering could deepen. Pein has a complex relationship with pain, and through his training, Naruto could gain a new perspective on it. This might make him more empathetic towards his enemies, or it could fuel his determination to end the cycle of hatred in a different way.
His character would likely be more aggressive. Demons are often seen as violent and forceful, and Naruto raised by them might adopt these traits. He may be quicker to anger and less likely to show mercy in combat.
His character would be more confident and assertive. Kurama's presence would give him a sense of self - worth from the start.
His character would become more brooding perhaps. Growing up in the Uchiha environment could make him more in tune with their emotions and vendettas.
Naruto would likely become more introspective. Indra was a complex figure, and Naruto would need to think more about the deeper aspects of power and responsibility. He might become less impulsive in his actions as he tries to live up to what he perceives as Indra's ideals.
If Naruto is trained by the Raikage in fanfiction, his character development would be significant. His sense of loyalty and determination would be further strengthened. The Raikage's unwavering commitment to his village and people could inspire Naruto to be even more dedicated to protecting his own. Also, Naruto would learn to be more patient. The Raikage's training methods might not yield immediate results, and Naruto would have to endure and keep working hard. This would teach him the value of perseverance. Additionally, his leadership skills could be enhanced as he observes the Raikage's leadership style. He would understand how to make tough decisions and lead by example, which would be crucial for his future as a potential Hokage.
His character development could involve him becoming more empathetic. Being mute, he would understand the struggles of those who are different or marginalized. He might start to advocate for them in his own silent way. Also, he'd have to work hard on his physical expressions and body language, which could lead to a more refined and nuanced way of presenting himself. His relationships with others would also change, making him more reliant on true friendship and loyalty rather than just words.