Thou shalt not groom Mary Jane
I really don't understand the examples you provide to "support" your points.Saban isn’t his own DC no matter how he has the staff structured. He’s had multiple DCs go on to be head coaches including the reigning national champ.
And calling plays is the least important part of being a coordinator? Tell that to EB.
I mean, in an argument where your general point is trying to say that successful head coaches generally don't run one side of the ball, you're the one who brings up Andy Reid?