BYU has a healthy starting Sr. QB. Usually, judging by past years, that bodes well. The offense in general appears to be pretty loaded, and the offensive line should be lots better. So, BYU should be able to score.
The biggest unknown is the defense. The defensive front 3 are OK, but not stellar. They are experienced, so we can hope for improvement. Bronson Kaufusi playing there instead of LB should be a plus. The linebackers should be solid, and possibly very good. The DBs have talent, but there are questions. With Bronco running the defensive show again, I'm optimistic for improvement over last year.
So, what is "realistic"? I don't know. I don't think you know. What past years should we use to judge? Probably none, since this is a new year with different challenges and different strengths.