Steve Kerr is the best of that bunch by a long mile ..
Steve Kerr learned the hard way as a GM with Rookie of the year Amare Stoudemire. And letting a puppet assistant coach Mike Dantoni get to much fame from Steve Kerr getting rid of the Phoenix Suns individual players Marbury & Penny slow balling poor defensive talent in 2003-4 season, to let their highest paid player Shawn Marion leadership run and control the Phoenix Suns roster (The Matrix got the SSOL system from Jason Kidd, and used that system with Steve Nash & Amare to have a few successful seasons.).
Mike Dantoni refusal to bring in assistant coach Thibideu in the 2007 offseason, had the owner of the Phoenix Suns trade Shawn Marion for Franchise Player Shaq on the February 2008 trade deadline, which put Kerr's GM job in jeopardy.
What we get in Steve Kerr is a GM/Coach who played the Triangle-system and won, plus defended against the Triangle-system and won.
Disagree and it seems like you're running things together here not distinguishing when Steve took over. I mean let's keep it real. Steve Kerr was brought into the Suns organization to essentially do what Phil intends to do for us. Yet Kerr failed and bailed as soon as he saw Phx couldn't win a chip with Nash and didn't want to be a part of rebuilding the Suns.