Naruto's bankai might incorporate his fox - like features. Given his connection to the Nine - Tails, his bankai could have a large, fiery fox form that enhances his speed and strength, much like how his Nine - Tails Chakra Mode works. His zanpakuto could also be related to the rasengan, perhaps having the ability to fire off rasengan - like attacks from the blade or using the spinning energy as a defensive mechanism.
In fanfics, anything is possible. Since it's a fictional creation, an author could write a scenario where Naruto has the ability to use Bankai. However, in the original Naruto and Bleach universes, their powers are completely separate, with Naruto having chakra - based ninja abilities and Bankai being a high - level power in the Bleach world.
In the manga, Senjumaru did not employ Bankai. The character's abilities and actions were depicted differently without resorting to this particular power.
Shinji did use his Bankai in the manga. It was a crucial moment that turned the tide of the fight. The Bankai's power and unique abilities were showcased, adding an exciting element to the story.
One popular bankai ichiruki fanfic might be those that explore their unique bond during intense battles. For example, some stories could focus on how Ichigo's bankai development is intertwined with his relationship with Rukia. They might show how their powers complement each other in ways not seen in the original series.
One interesting 'Naruto Senbonzakura Bankai' fanfiction could be one where Naruto somehow gains the power of Senbonzakura Bankai and has to learn to control it. He might face off against powerful enemies in new and unexpected ways, using the unique abilities of the Bankai.
In a Naruto achieves bankai fanfiction, it could happen through some sort of cross - over magic. Maybe a powerful jutsu misfires and transports Naruto to the Bleach universe where he somehow gains the ability to achieve bankai. It could also be due to a powerful being bestowing this power upon him in an attempt to create a powerful ally or as part of a grand experiment.