One interesting storyline could be about the tailed beasts forming an alliance outside of the control of humans. They might work together to protect their own kind and the world in a different way than the shinobi. For example, they could create their own hidden land where all chakra - based creatures are welcome.
In this fanfiction, Naruto could control all the tailed beasts because of his unique chakra nature. His chakra is very special and has a high compatibility with the tailed beasts' chakra. Also, his experiences with Kurama might have given him insights on how to handle other tailed beasts. He probably communicates with them on a spiritual level and convinces them to work together with him.
Well, in many fanfictions, Naruto might use his strong will and the power of his Uzumaki heritage. His natural chakra reserves are huge, which helps. He also has a deep understanding of friendship and the tailed beasts' pain from his own experiences. So, he can connect with them on an emotional level and gradually gain their trust, thus being able to control them.
Another way is through shared experiences. If they face a common enemy together, like an evil organization that wants to capture all tailed beasts, they would have to rely on each other. This would lead to deeper understanding and stronger relationships as they fight side by side and protect one another in the face of danger.
Sakura could be a great help. Her medical skills could come in handy if Naruto gets injured during his battles or difficult encounters while trying to free the tailed beasts. Also, her combat skills have improved over time, so she could fight alongside Naruto.
In many fanfictions, the tailed beasts' personalities are shaped by their experiences. The Five - Tailed Horse is usually depicted as noble and proud. It has a certain elegance in the way it behaves. The Six - Tailed Slug is more nurturing and gentle, perhaps because of its slug - like nature. The Seven - Tailed Horned Beetle is often seen as mysterious and a bit aloof. It keeps to itself and doesn't easily open up. When it comes to the relationship with Naruto, these personalities play a big role. For example, Naruto might have an easier time getting along with the more friendly - natured tailed beasts at first, while having to work harder to understand and befriend the more reserved ones.
Madara Uchiha could be a great antagonist. His powerful Sharingan and vast combat experience would make him a formidable foe against the Nine Masked Beasts. He could be after their power to further his own plans for the ninja world.
One interesting concept could be the unique bond between the Naruto characters and the beasts. For example, how they communicate and work together in ways not shown in the original series. Another could be new forms or powers that the beasts might have, which add a fresh twist to the story.
The relationships can be developed through shared battles. When Naruto and the fem tailed beasts fight side by side against common enemies, they can start to trust each other more. For instance, if they face a powerful rogue ninja together, they'll learn about each other's combat styles and strengths.
Well, it would drastically change the power balance. Naruto already had a strong connection with the Nine - Tails. Having 3 tailed beasts would make him an even more formidable force. His enemies would be much more cautious around him. He might also have to deal with the different personalities and powers of each tailed beast, which could be a challenge to control all at once.