Sounds like an excellent choice in spite of your preference for Sheriff Andy or Barney.
Critics who whine about him being a right wing ideologe convince me that he is EXACTLY what is needed there. His enemies are my enemies.
None of the prerequisites you note him lacking are relevent to administering a huge bureaucracy. J. Edgar Hoover was just another lawyer when he was named head of the FBI. I doubt that any experienced lawman could have done as well as he.
This is a phenomenal pick. Chertoff is TOP DRAWER. Brilliant, engaging, has worked the press in the past, good conservative credentials, but not an ideologue. Bush could not have made a better pick for this post.