Naruto is likely to be popular too. Even though it's a Boruto x Sasuke fanfic, Naruto's relationship with both of them is so important. He could play a role in supporting them from the sidelines or even getting involved in a crucial part of the story.
One interesting plot could be Sasuke taking Boruto on a special training journey across different hidden villages. This would not only strengthen Boruto's skills but also give them a chance to bond like master and apprentice.
Sasuke often appears in different story arcs of the Boruto manga, depending on the current plot and mission. Sometimes he's on a solo mission, sometimes he's involved in events related to the village.