TCU is also a private religious school with an undergraduate enrollment of around 8,400 people, which is notable mostly because of how it affects your walk-on program (i.e., hurts not helps). Not as challenging as Rice or Tulsa, but it's not like being the state school in SEC territory, either.
The real issue with Patterson is one of fit. I don't think he wants to coach in this area of the country. There is also age to factor in, as well as the relative expectations of where he is now -- i.e., they won't kill him over a 4-8 record every once in awhile -- versus that of a school like Alabama. I've also long wondered whether he was/is friends with Franchione, and I don't know the answer to that question. But if he is friends with Franchione, it would make attracting him to Tuscaloosa very difficult. On both sides.
If Saban had left prior to this year, I would have made Jim Harbaugh tell me "no" first, then I would have pursued McElwain. Saban is very unlikely to coach beyond 70, in my opinion. I think by that time, McElwain will have a sufficient body of work and you'll see Alabama and Florida in a major war for his services. If McElwain isn't an option, you can start by looking at any other coach with Saban connections and prior, successful head coaching experience (meaning, Fisher would be in play), and if no one from that group is available, begin looking at whoever is an assistant on Saban's final UA staff. I am virtually certain Alabama will hire from the Saban coaching tree when he eventually leaves.