As for altering the subjects to get what we are after, or staging, perhaps if the shot doesn't "appear" staged, then we have successfully achieved our goal.
Remember a motion picture (movie) is an entirely staged event, but that doesn't mean the emotion and magic between the people isn't real and doesn't necessarily affect us as spectators any differently than a real event. There were a lot of people crying during the movie Titanic. And some for the right reasons. Obviously some because they could never get those 2 hours and their money back.
In Gene's(*) photographs there is something which throbs, something always tremulant. They are taken between the shirt and the skin. Anchored between the shirt and the skin – at the heart – his camera moves even by its passionate integrity. - Henri Cartier-Bresson - (* W. Eugene Smith's)
Eye contact is a magical thing.
Is there a different impact to the photograph.
I have an interesting thing I do while doing portraits. The body is set, the lighting is set and everything is set. Then I just talk to them. I do this a lot with kids. I just ask questions about them, their pets, their girlfriends/boyfriends, etc.......The shot is staged, obviously. But their mind isn't. It's moving and reacting. The wheels are turning. And the facial muscles and eyes are reflecting that.
I do this with adults sometimes. Everything is set. Then I say, think about this ???. Then think about your first kiss. Think about your last birthday, think about your deceased father....etc etc. Same thing. Stages shot but the mind is moving. Emotions are coming out. Sometime they cry, or laugh or they get melancholy or whatever.
With brides and fathers I used to manipulate them by getting them to look into each others faces and maybe half the time the father would start to get teary eyed.
The shot of VE day with the sailor and the nurse ( I think it was), could be setup just by telling the guy to "dip" her. Total setup. But the emotions that they then exhibit are real.
Staging is interesting.