Yeah, if you add enough qualifiers to it, there is no precedent. But that's disengenuous. There is a precedent for successful NFL coaches not being successful in CFB. That's not really arguable unless you want to shift the goalposts.
The only disagreement I have here is the last sentence, really. Yeah, NFL coaches work a lot, but they do have a lot more time in the offseason they can spend away from their job. College coaches are basically always on the clock in some way or another.
Even when they get some vacation time away with the family, they've gotta pick up the phone if a 5* or a key commit calls. Even during dead periods, they've gotta do evaluations of recruits and keep half an eye on the kids on campus.
NFL coaches have to do evaluations for the draft and all, but they've got a GM sharing that load and times during the offseason when they can get away uninterrupted for a while at least.
The academic ineligibility thing was just an example of some of the things NFL coaches don't have to deal with that college coaches do. My ultimate point this whole time has been that no amount of NFL success can really guarantee college success because of the many small differences between the two.
I think Gruden would be a good coach as well. I'm not sure he'll be the Saban killer many hype him up as, but I don't doubt he'd recruit really well for us, put together a good staff, and develop talent much better than we've seen in a while.
If he's gonna be as good as many here are hyping him up to be though, we'd need to surround him with a crazy large support staff like Bama has done with Saban.
My bad I thought your post had an aggressive slant to it. Tone can be hard to nail over the internet.