My husband is ex-military and very calm in an emergency. I can't imagine a better person to assist with an evacuation, but he does not have the status to select exit row seats. My sister's husband has top status on Delta and always sits in the exit row; however, my sister says he would open the door but would just be the first one out. So you can never tell what type of person would be sitting at the exits in an actual emergency.
Even if there were training, no one knows how any person would respond when a real emergency occurs. There are many stories of FA's reacting to an emergency with panic and tears even though they have had extensive training.