I'm a Lakers fan, and I agree with you on Van Exel being lazy. But screaming at a player when you're on your first game as a head coach was a bad look. I knew he wouldn't make it. Larry Bird is another good example. While he was much more calm than Magic, if you paid attention to his timeouts you would see assistant Randy Whitman coaching up the players while Bird listened in.
As for football position coaches, Mean Joe Greene was mediocre and Charles Haley was just bad. If you look around, you'll see a lot of that with the great players. Two Sooners I thought would get into coaching (and maybe they have) are Curtis Lofton and Rocky Calmus. Lofton was a good (not great) NFL linebacker, but his instincts while calling the defensive plays were impeccable. Calmus didn't have the size to play in the NFL (tried gaining weight but that just led to injuries), but other than Bosworth, has OU ever had a more instinctive linebacker? I would imagine both would have the right disposition to be effective position coaches or better.