First off you are probably cannibalizing your best feeder school for in-state talent. Lewis finds them and develops players that can seamlessly adopt Rose' offense.
Lewis is basically on par with Tim Lacomb on the staff as far as coaching ability. You're not really getting an upgrade as far as coaching is concerned IMO.
You need to replace Pope with another 'big man' coach that can recruit. Preferably a coach that can recruit outside of Utah. Rose has a big name in the NCAA coaching circles now. He should be able to bring in a good LDS or non-LDS coach wanting to learn his approach and progress in their careers. Rose has a great track record with his assistants moving on to HC positions. BYU needs to think bigger than Lewis IMO.