Week 1 - The week between TCU and Houston they have to implement a game plan. Could they make a tweek or two to some plays? Sure. Could they implement a new offense? No. No chance. So this week doesn't count as far as "implementing an entirely new offense" (that's the post of mine that you originally replied to.)
Week 2 - The bye week. They've got 7 days. Most new OC's at a school use the first 4 weeks of spring practices to implement a brand new offense. And even then - they don't have the whole offense down and are counting on using fall camp to refine things. So - could they implement some new plays? Tweak some of the old plays? Yes to both of those. Could they "implement an entirely new offense"? Learn a whole new playbook? No way. Not in one week.
Week 3 - Game week with BYU. They've got 7 days again. Now they are trying to practice the plays against the scout team that is running BYU's defense. They don't necessarily have time to implement an entirely new offense - they have to focus on BYU's defense too.
I mean - if Utah decides they want to use these two weeks to focus on implementing a brand new offense and learning new plays instead of learning how to read BYU's defense and play against it - that would be a best case scenario for BYU. Because the Utah players would be so focused on what to do with their own new plays that they wouldn't have any time to look at what BYU does and I really like BYU's chances to blow up most of Utah's offensive plays in that scenario.
I know they have three weeks of time since the new OC was named. I'm saying that they don't have that much time to implement an entirely new offense. Because some of the time during those three weeks was used to focus on what Houston's defense does and what BYU's defense will do. They don't get to just learn their new plays in a vacuum without knowing how to run the play given the defense they face.