Hi Simon,
It probably won't surprise you that I find this thread both fascinating and helpful.
As you know, I'm no expert, in fact currently a step behind you on the practical side of things, but I have also read/viewed a lot of theory recently so please (everyone) bear that in mind in my 'critique'/analysis below.
I am guessing, from the reflections in Zena's eyes in #1 and #3, that the key light was a small flash pointed up, with a largish bounce panel/umbrella behind it, directing some light forward on to the subject - I say this because there's a small bright catch-light below a dimmer, larger one, which may be circular, but this is hidden by her eyelid.
The light in #1 is very even across the face - how many light sources were there?
Just the Key (almost above/behind the camera) and hair-light?
The hair-light is quite low relative to her and lighting a lot of her neck and even under her chin (same in #3) which doesn't seem natural to me.
I prefer the composition of #3, showing more chest than the horizontal format ones, where she feels 'cut off' at the neck. In #1, this also leaves me thinking her eyes are too low in the frame.
However; you did say "not that I got to play with light placement too much" and a lot of the issues I have raised relate to that aspect.
The other thing I take away is that the WB is quite different between #1 and #3 - looking at the whites of her eyes in #1, they may have a slight green cast, whereas #3 looks rather yellow - I note AWB was used.
I have picked up on a lot of negative things there, but I can quite understand how I might feel 'overwhelmed by the moment' of suddenly being in a position to shoot a real human and all the theoretical research suddenly deserting me at the very moment it is needed most.
... and posing is something I haven't done enough on either.
Thanks, Dave
EDIT:
I guess, like any other element of being prepared for any shoot, it is a case of thinking about it ahead of time - and having a few poses identified in our minds to capture. This is definitely something I would not have done, had I not read your post.
Now I need to think about it, the first thought that comes to mind are;
a) hands crossed in front of body - e.g. if sitting backwards on a chair or looking over a fence/divider/piece of furniture, head could be on hands, or these might be lower in the frame.
b) If a stool is available; hands on legs
With both these, we'd need to beware Depth of Field issues and 'fore-lengthening' if shooting from too close (i.e. with too short a lens focal length)
c) Or perhaps use a more overt 'prop'; may be a mobile phone; pretend call or texting, with appropriate facial expressions - this idea means the eyes wouldn't be looking at the camera though