I think Yamato could be a good choice too. His ability to control wood style could be really useful in the past. Maybe he could time - travel to help with the growth of the first trees in the ninja world or something like that. And his calm and collected nature would help him adapt to the new situation in the past.
Self - discovery is a significant theme. When Naruto travels back in time as an ANBU, he sees himself and the world around him in a new light. He discovers new aspects of his abilities and his personality. Additionally, the theme of secrecy and trust is common. As an ANBU, he has to keep his identity and mission a secret, but he also has to figure out who he can trust in this new timeline. This adds a layer of mystery and tension to the fanfictions.
A common theme is redemption. Naruto often goes back in time to correct his past mistakes or the mistakes of others. For example, he might try to save a character who died in the original timeline. Another theme is power - growth. Since he has knowledge from the future, he can train more effectively in the past and become even stronger.
I really liked 'Anbu Naruto's Time - Twisted Adventure'. In this fanfic, Naruto goes back in time and joins the Anbu much earlier. It's full of action and there are some really cool fight scenes. The author also does a great job of exploring how Naruto's time travel affects the relationships he has with other characters.
One possible scenario in such a fanfiction could be that the Anbu Commander travels back in time to prevent a major tragedy in the Naruto world. Maybe he goes back to stop the Uchiha massacre. He could use his knowledge of future events and his Anbu skills to change the course of history.
One great 'naruto anbu time travel fanfiction' is 'Naruto: Time Travel and the ANBU'. It has an interesting plot where Naruto goes back in time as an ANBU member and tries to change things for the better. Another one could be 'ANBU Naruto's Time - Travel Adventure' which focuses on his experiences in the past while being part of the ANBU and how he uses his knowledge from the future.
His character could become more cynical at first. Seeing the past and all the wrongs that were going to happen might make him question the world more. But as he starts to make changes, he might regain his optimism.
One potential main antagonist could be an older, power - hungry shinobi who has infiltrated the Anbu in the past. This shinobi could be jealous of Naruto's sudden rise in the Anbu (due to his future knowledge) and sees him as a threat. He then starts to plot against Naruto and the Anbu's new - found positive direction. Or perhaps it's a corrupt politician in the village who uses the Anbu as a tool and doesn't want Naruto to change the Anbu's loyalty from him to the village as a whole.
One idea could be that Naruto travels back in time and joins the Anbu at a young age. He uses his future knowledge to prevent certain tragedies within the Anbu, like stopping betrayals. Another could be that he travels back to change the fate of a particular Anbu member he befriended in the future. Maybe he tries to stop the Anbu from being misused by certain corrupt elements in the village.
Their relationship might become stronger. Going through time travel together, facing new and old challenges, would force them to rely on each other more. They would see different sides of each other and gain a deeper understanding.