Saban has also fired a very good recruiter and position coach, for lying to the NCAA(and Saban) about breaking the bump rule. He has given several questionable guys a second chance, see Kiffin, Sark, Locksley, the kid from UGA(that he kicked out as soon as he was accused again, even though the accuser later recanted).
There is no comparison between the college game and the NFL, so don't try to make that argument. Hell, if he had gotten what he wanted, in Drew Brees(the doctors told him he would never recover), he may not have failed at that level, he was only there two years anyway. He improved them in his first year. Guess what, Landry did not start out too well, neither did Belichick or most any legendary NFL coach. We have zero idea if he would have turned it around. I doubt he would have, as he hated the job. (insert your reasoning here).
No coach in history can stop all the booster shenanigans. They can make them be more "on the sly" about their dealings, so exact details do not get back to them. FWIW, I have not heard nearly as much bragging about the handshakes as when Shula was still the coach. Does not mean it has stopped, just that they are being more careful.