One interesting plot could be that Naruto discovers his hidden bloodline gives him the ability to control time in small increments. This allows him to dodge attacks more easily and plan his counter - attacks more effectively.
It could be a rogue ninja from a forgotten clan who is jealous of Naruto's new - found power from his hidden bloodline. This antagonist might try to steal Naruto's bloodline ability for himself.
It could also be a result of a unique encounter with a powerful entity. For instance, if Naruto entered a mysterious realm where the essence of Haku's bloodline was stored, and some sort of transference occurred, perhaps due to Naruto's own unique chakra nature. This could lead to him obtaining Haku's bloodline.
Power discovery. Since the Uzumaki bloodline is powerful, a common theme is Naruto finding out about his hidden powers. For example, he might discover a new form of chakra control or a special jutsu related to his Uzumaki heritage.
An orphan with no known family could be the main character. They discover they have a hidden bloodline through a series of events. It could be a bloodline that gives them the ability to see the past or future in dreams. This character would then be on a journey to figure out where they came from and what their power means, all while trying to fit into the ninja society.
Well, it could be about creating unique storylines within the Naruto universe that focus on the hidden bloodline abilities. Maybe it's a challenge where fans write about how characters with rare bloodlines face different trials or how these bloodlines are discovered and developed in new ways.
A really interesting 'naruto has uzumaki bloodline fanfic' is 'Naruto: The True Uzumaki'. This fanfic explores the political implications of Naruto having the Uzumaki bloodline. It shows how different villages react to the fact that Naruto has such a powerful and rare bloodline, and how Naruto has to navigate through all the politics while still being true to himself.
There are also fanfictions where a bloodline is created through some sort of experimental jutsu. For example, a bloodline that allows the user to transform into different elements at will. This would give the character an edge in combat as they could adapt to any situation by changing their form.
A really interesting plot could be a character who discovers they have a bloodline that is a combination of two powerful clans' abilities. This creates a unique set of powers that no one has seen before. The character then has to struggle with learning to control these powers while also facing the jealousy and fear of others in the ninja world who see them as a threat.
In some fanfictions, one of the bloodline limits could be something like a super-enhanced Sharingan-like ability. Another might be a power related to controlling natural elements in a unique way, for example, a more powerful form of water control. And perhaps a bloodline limit that gives Naruto the ability to instantly teleport short distances. However, different fanfictions can have very different interpretations of these six bloodline limits.