Obviously, he would be better than what we have today, but I think we'd be setting ourselves up for disappointment. The college game has changed a lot since Stoops stopped coaching (2016). He never had to deal with the current transfer rules or NIL. It wouldn't be an overnight turnaround.
That being said, he's the only coach on the planet with an NCAA Championship and an XFL Championship, so nobody else would have a coach with that accolade.
Speaking of XFL, I think that's a big reason he'd never do it. Unless he's into coke, gambling, or hookers, he made enough money at OU that he never has to work again. I think the XFL gives him a low to no pressure way to stay around the game and probably scratches any itch he has to coach. If the XFL folds, there are a million other places for him to scratch the itch without being the CEO of an SEC program. I could be wrong, but I don't think he has any desire to come back to the high stress world of Power 5 college football.