Well not be disagreeable but I don't think any of those three are 1st tier coaches. I think of 1st tier as Gruden, Saban, Stoops, Chip and Brian Kelly, Carol etc. I agree they may be good coaches but with any of them we are looking at 6-8 years to compete. That's if they are good coaches. They will be lucky to have top 15 recruiting classes in their first few years, which is middle of the pack for the SEC. If they win 7-8 games their first couple of years and show improvement the recruiting could improve and by the third or fourth years their recruiting classes could break the top ten. Those classes will have to be at least sophomores or juniors before they can be expected to contribute. This means 6-8 years before you're challenging for the east.
The alternative is to hire a superstar coach that will land 5 star recruits from day 1. It really reduces the rebuilding time.