You can be a mid G5 coach, and take the step up and be successful. What comes to mind are guys like Jim Tressel (Youngstown St. directly to a natty at O$U), and Urban Meyer (from Utah in the Montain West conference to a natty at UiF), and Jim Harbaugh (from U of San Diego in the Pioneer League to Stanford at a top 4 BCS finish).
If you have it, you have it.
But it's just like evaluating players. Rankings and stars don't guarantee success. And where the AD's fail, is that they focus to much on the numbers, and not enough on the intangibles that allow a coach to be successful, and set up the program accordingly.
Your example of Al Golden Shower is perfect. A guy who interviews well. Says all the right things, can plan and is organized, but if you dug deeper into him, you would have seen the deficiencies that made him wrong for UM. Even if he was a coach with a history at power 5 and in the NFL, he'd still have those holes in his game. Not easy to spot, and given how weak our AD was at the time, it was a disaster waiting to happen.
Uhhhh...no.
Jim Tressel was not a "mid G5 coach". He won four national championships in Division I-AA. Tressel would likely have been offered the Miami job earlier than the Taint job if not for some of his issues.
Urban Meyer took that "Mountain West" team to a final #4 AP ranking and the Fiesta Bowl. Florida secured his services over interest from Notre Dame.
Jim Harbaugh had helped his father coach college football for years before spending two years at San Diego BEFORE GOING TO STANFORD. Before Michigan.
Billy Napier won the Sunbelt once, legitimately (and once by default). He got his Louisiana teams to the "First Responder Bowl" and the "New Orleans Bowl". Nobody was competing against Florida to hire Billy Napier.
Please, for the love of God, do not EVER compare Billy Napier to Jim Tressel or Urban Meyer or Jim Harbaugh. There is no comparison.
The issue is not whether a coach has ever spent time at a G5 school. Your context-free citation of the names of three future College HOF coaches does not suddenly render Billy Napier a "good hire" or a potentially great coach at the P5 level.
The issue is that prior to hiring a coach at a very high-level P5 program (and, yes, I hate the Gaytors, but they HAVE won national championships recently), a G5 coach had better do something pretty special to merit that consideration and promotion.
Tressel was a great I-AA head coach. Perhaps one of the greatest I-AA coaches of all time.
Urban Meyer head-coached at TWO lower-level programs prior to Florida. He worked his way up by proving himself twice. There was serious competition to hire him.
Harbaugh worked his way up through both the NFL and college ranks, and was a head coach at a lesser P5 school before joining Michigan, his alma mater.
Billy Napier is none of those things. He's a guy who got a shot at a G5 program after looking good coaching Mario's recruits. He had a couple of good years, but the P5 wasn't beating his door down.