As a mom of 3 BYU students who got in with scholarships, I think the essays are hugely important. They can only get to know your student by what you include. If most of his good stuff is work-related, try to find different attributes he has learned along the way. Did he have a particular experience where he learned new skills? Where he had to really perservere? A time when he had to work with another person and it was particularly challenging or where he learned a lot? How does he feel about helping his family or community by his work? I think there are a lot of angles he could come from.
He could also talk about hobbies that maybe you'd think aren't as impressive. Does he like to read? Go for walks with friends? Connect with ward members? Minister within your ward or family?
He could also talk about things he did make time for, even if it was for a short period. What impact did it have? And how does it relate back to the aims of BYU. We've had family friends write essays about how they were tall and how that changed how people treated them, how they like to journal, or even silly things they did with friends. Let the BYU admissions people get to know your son from many angles.