Well, it could be that Sasuke has a personal goal that she believes is more achievable if she is perceived as a male. For example, she might want to rise to a high position in the ninja hierarchy, and historically, it has been more difficult for women to reach the top in that world. Also, she may be trying to fit in with a certain group or ideology that is more male - dominated. By hiding her being a girl, she can more easily blend in and pursue her dreams without the hindrance of gender - based discrimination.
There might be a character who serves as a sort of antagonist in relation to Sasukw's secret. Maybe someone who is trying to find out the truth about her for their own reasons, whether it's out of jealousy or just a nosy nature. This character would add conflict to the story. And of course, there could be a love interest, someone who Sasukw has feelings for but can't fully express because of her hidden identity.
Hey, I recommend you a novel called Naruto's Daughter Sasuke. In this novel, the female lead, Sasuke, was a tough, unyielding, brave and strong girl. She experienced hardships in the Naruto world and became an excellent ninja, guarding the Kinoha Village with other ninjas. I hope you like this fairy's recommendation. Muah ~π
One possible interesting plot point could be the challenges Sasukw faces in maintaining the secret. For example, she might have to constantly be on guard around certain characters who could potentially expose her.
On the other hand, Sasuke could be worried. He may think that Naruto is in some kind of trouble or danger. Given their history and the care they have for each other in the SasuNaru dynamic, Sasuke's concern could lead him to be more protective. He might start investigating the situation on his own to figure out why Naruto is hiding his face and ensure his safety.
It could show that Sasuke becomes more protective of Naruto in secret. He might sense something is different about her but not be sure what. This could lead to some tense yet tender moments between them as he tries to figure it out while still respecting her privacy.
Perhaps he has hidden the full extent of his Sage Mode abilities. He might be able to stay in Sage Mode for a much longer time than he has shown so far, or have some other undisclosed powers within that mode, like the ability to sense enemies from much greater distances.
In a fanfiction, Sasuke and Sakura might be protective of Naruto in a more emotional sense. For example, when Naruto is doubting himself due to some rumors in the village. Sakura would be the first to stand up for him, using her sharp tongue to put the rumor - spreaders in their place. And Sasuke, in his own quiet way, would show his support by training with Naruto extra hard, as if to remind him of his strength.
The most obvious consequence would be the end of their iconic friendship. It would change the whole dynamic of the story. For Sasuke, he might feel lost or even a bit angry that Naruto, who was always there for him, is now indifferent.
One consequence could be the change in his relationships. His friends might react in different ways. Naruto, for instance, might be initially shocked but then become more protective. His enemies could also underestimate him thinking that the transformation has made him weaker. Another consequence is how he views himself. He would have to adapt to a new body and different social expectations that come with being a girl in the Naruto world.