In the fanfiction, Gaara might gain new powers along with getting Shukaku back. Maybe he'll have better control over sand abilities, as Shukaku was a source of his power before. He could also use Shukaku's strength to protect his village more effectively.
One popular theme is the relationship between Gaara and Fem Shukaku. It could explore how they interact in a world where Shukaku has a female form. Another theme might be the power dynamics. Since Shukaku is a powerful entity, in a fanfiction, it could show how Fem Shukaku's power affects Gaara's life and his role in the village. Also, themes of friendship and mutual understanding often come up. As Gaara has had a difficult past, Fem Shukaku could potentially be a source of newfound support and a different kind of connection for him.
His friends would be affected. They might be both in awe and a bit worried about the new - powered Gaara. His siblings, too. They would need to adjust to this new version of Gaara who has Shukaku back.
It's a complex web. The Shukaku's presence and the Sharingan play significant roles in shaping Gaara's experiences and potentially influencing his love story.
The canon relationship between Gaara and Shukaku is very much about Gaara suppressing the power of Shukaku. However, in fanfiction with Fem Shukaku, their relationship could be based on mutual growth. Fem Shukaku could teach Gaara different ways to use and understand his power. Their interactions might not be as combative as in the original story. Instead, they could be more about sharing knowledge and experiences. For instance, Fem Shukaku might have a different perspective on the use of chakra that she could share with Gaara, leading to a new dimension in their relationship.
A simple fanfiction could be that the female Kyuubi and female Shukaku start to communicate telepathically across different worlds. They realize they have more in common than they thought and decide to help each other. The female Kyuubi could offer some of her power to help the female Shukaku control her more chaotic tendencies, which in turn benefits Gaara.
One possible fanfiction could be about the female Kyuubi and female Shukaku forming an unlikely alliance. Maybe they team up to help Gaara and Naruto in a battle against a common enemy from the FF7 universe. It could explore how their unique powers interact in this crossover scenario.
The other Jinchuurikis could be potential allies. They understand the struggles and the power that comes with having a tailed beast inside them. For example, Killer Bee, who has a good relationship with his tailed beast, could share his insights on how to better co - exist with Shukaku. Tsunade might also be an ally, as she is a powerful Hokage who could offer protection and resources to the Jinchuuriki.
I would recommend 'Naruto and Shukaku: A New Alliance'. In this fanfiction, it focuses on a scenario where Naruto and Shukaku have to team up against a new, powerful enemy. It has a lot of action scenes and also some really interesting character development for both of them.
Good fanfiction in this regard also pays attention to the lore of the Naruto universe. It should be consistent with the rules about chakra, jinchuriki, and the world - building already established in the original series. If it just ignores all these elements, it won't feel like a proper 'naruto and shukaku' story.