I know this has about as much of a chance of happening as a snowball's chance in hell, but if Jimmy Johnson were to be lured out of retirement by Jerry, how would you feel about it, and what would be the result.
5 years $60 Million might do it.
Going with your premise (rather than just saying he'd never do that), I'm not sure that Johnson would have the same kind of success he had in the 1990s. There was a lot that went into our success then, including the Herschel Walker trade, the lack of a salary cap and limited free agency.
He was not able to duplicate his success in Miami despite having Dan Marino. (He did make the playoffs three out of four years, though.)
I do think our defenses would be better under him and that he deserves more credit than he probably receives for how good our defenses were in the early 90s. I'd be interested in seeing what he could do even though my expectations would not be for him to produce Super Bowl victories like he did when everything lined up right the first time around.