Rangnick would be a mad appointment. Maybe not the absolute bottom of the barrel but pretty bad I would say. I think a lot forget just how funny it was when he was United manager, it was like Solskjaer, but maybe worse actually? Practically the same, but certainly felt worse at the time. He was really good at finding new ways to humiliate them.
It wouldn't be bad. Have you seen what he has done with Austria? He is a good manager and his stint at Man Utd was the outlier in his career and it was expected, because neither him nor the club were committed to it. Rangnick needed a job and probably wanted to get some publicity, the club needed someone to sit on their bench for half a season. That's why he cut all ties once he got the Austria-offer and the Mancs were happy not to have to pay him as a consultant. Rangnick is still highly respected in Germany and I could see him doing well with Bayern. Only questionmark I'd have about him at Bayern was whether he could deal with the pressure there and constant media stories about him and the club.