The bloodline can be developed by exploring its limitations. For example, maybe there are times when the 'heartless' nature actually becomes a weakness, like when trying to form alliances. Another way is to expand on the powers. Maybe the character can use their heartless state to enter a special dimension or communicate with dark entities.
One interesting concept could be how the heartless bloodline affects the character's relationships. For example, it might make them more isolated as others fear their power. Another concept could be the unique jutsu or abilities that come with this bloodline. It might allow for some really cool and unusual combat techniques that set the character apart from others in the Naruto universe.
Well, in some fanfictions, Naruto might control the heartless through his strong will and the power of his chakra. Maybe he uses some new jutsu he developed specifically for this purpose.
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.
Perhaps a dark power corrupts him. In the fanfiction, there could be some sort of dark chakra or evil entity that latches onto Naruto. This entity could slowly eat away at his emotions, starting with his heart, making him gradually lose his ability to feel empathy and turn heartless.
No. Naruto is known for his kind heart and strong sense of justice. In the original series, he always tries to understand his opponents and save them rather than being a heartless killer.
The knight bloodline could be integrated as a foreign power that was brought to the Naruto world long ago. Maybe a group of warriors from another dimension with the knight bloodline came and settled, and over time their bloodline got diluted but still resurfaces in certain individuals.
He might use some special jutsu or seals. For example, he could use a sealing technique to suppress the signs of his bloodline. This way, others wouldn't be able to detect it through normal means like sensing chakra.
It could also be part of a strategic move. By hiding his bloodline, he can surprise his opponents in battle. They would underestimate him based on not knowing about his true powers, and then he could turn the tables on them when the time is right. This gives him an edge in combat situations.
Well, one implication could be enhanced physical abilities. Dragons are often seen as strong and powerful creatures in many mythologies. So Naruto might have greater strength, speed, and endurance. He could also have some sort of elemental control related to dragons, like breathing fire or manipulating wind in a more dragon - like way. Maybe he could even fly in some forms, as dragons are known for their flight ability.