Most importantly, he is an incredible recruiter. Utah has owned BYU in state lately, especially for polynesian trench players. Much of that success is due to Sitake.
He would get back to the basics, focus on football, and wouldn't push the religious element like Bronco does. In other words, his approach would be more like Lavells.
He is a fantastic D coordinator/Assistant Head Coach at a good P5 program with an elite defense. He has trained under one of the nations best defensive minds, Kyle Whittingham , for the last decade, and is having phenomenal success this year in what is possibly the best offensive PAC ever. He gets the most out of his players.
Sitake knows how do develop kids and send them to the NFL. His defense has sent a constant stream of studs to the league, and I believe that his presence would mean the same for BYU.
He is an extremely likeable, charismatic, upbeat dude. HE always has an incredible attitude. Players and recruits love him. If I remember correctly, he was the first Tongan assistant coach, and that is huge in recruiting.
He knows Utah inside and out, and may finally give BYU a chance to be competitive in the rivalry again.
He still loves BYU.