First I'll say that Garrett is pretty much the given that he's going to be the next coach. At this point, and I'm keeping an open mind to this depending on how he handles himself as OC the rest of the way this year, I'm not sure that I like that option much anymore.
Now if I could have any available coach when it gets to that I've made it pretty clear that I'm a huge Cowher fan and that would be absolutely awesome, IMO. I still don't believe, however, that a guy like Cowher (Won a Superbowl and could land pretty much any opening that comes up that he wants) is going to come here and deal with the Jerry Jones that everyone believes he is.
If Jerry really is one of those guys who tells coaches who to play, when to play them, how to play them, what to do with the play calling, then I don't see a guy like Bill (Though I still can't for the life of me understand how any self respecting coach would either) ever being willing to take this job.
Outside of Bill, in terms of who might be available, Mike Holmgren could be a possibility, if he were interested in just getting right back into coaching and simply wanted a change of scenery from Seattle. He's got a good track record, as far as winning, getting to 3 Superbowls and has a W in one. I wouldn't be upset if he were the next coach, but something tells me he intends to take at least one year off and even if he didn't that San Fran job might be a lot more attractive to him since he and his wife are building a home in that area anyway.
Spags for the Giants would be an interesting possibility because he's a defensive guy, which this team badly needs if Wade isn't going to get the job done, but he'd be a rookie at it and that might be a draw back to the HC position. Still if Garrett is likely then Spags would warrant some consideration because you're effectively killing two birds with one stone. Getting a HC that could help this defense, the way Wade was supposed to, and taking an important coaching piece away from the rival GMen.
Around the rest of the NFL there isn't much else out there that I really care for, at least that I know would be available, as of right now.
On the college ranks...probably no one, honestly. I'm very leary, anymore, of college coaches coming to the NFL because of just how many fail, and fail spectacularly, anymore. I'm not a fan of the idea of bringing in Stoops, I've been hearing that where I live for a few years now. Everytime there is the rumors, or whispers, of Dallas being close to possibly needing a new HC the talk around here will turn to, "Will Jerry try and get Stoops." No thanks, I'll pass.