I'd say most of those are valid points. But I don't see any better candidates than Whisenhunt (which I'm guessing is why you said you're not excited about anyone). He was the OC for the Steelers when they won the Super Bowl in 2005 and Roethlisberger was ONLY in his 2nd year.
Also, when the Cardinals made the Super Bowl, it had been 9 years since Kurt Warner had won a Super Bowl,. And after Warner left you're expecting him to develop guys like Derek Anderson, John Skelton, Max Hall, Ryan Lindley, Brian Hoyer, and Kevin Kolb. Kolb is the only one of those 6 QBs that has a decent amount of talent. Leinart couldn't even start a game after Warner left (he got beat out by Derek Anderson).
So while Whisenhunt did get some help and make some mistakes, I hope he's the next head coach of the Lions. And I'm sorry if I attacked your answer too much. I'm glad to know what some of the negatives are, because no one had presented them yet.