What I really enjoy about BPL is the depth of investigations carried out by members - this is what makes this site so rich in value, knowledge and entertainment.
There is also another part of me that thinks that a great many of these sorts of enquiries are purely academic. They're an important component in product process, leading to further R&D and innovation and perhaps marketing edge, but sometimes they confuse me and stifle my decision making process...cause at the end of the day, they don't make much real difference. I do acknowledge that the OP referred to 'theory', and I think this is the operative word. But, the OP did ask for opinions regarding different foot boxes...so here is mine.
I personally believe that the shape of the footbox doesn't make much difference in real world conditions. Whilst the concepts and their arguments are sound on paper, I feel that once applied in practice, the intricacies of many of these issues fall by the way side.
I have several bags with all types of toe-box configurations (WM, ZPacks, Marmot, MacPac), and I can't really find a preference or value in any shape at all. They are all comfortable and warm (when I personally create the conditions for whole-of-body warmth while in a sleeping bag), and serve their purpose well.
As soon as I decide to.....
1. curl on my side and shorten my overall body length
2. wriggle my feet and alter the configuration of my toe-box
3. cross my legs and place pressure in alternate locations
4. have a stretch (see point 2 & 3)
5. wear socks...or not
6. wear thermals...or not
7. eat a proper meal and remain hydrated...or not
8. wriggle down the bag a little too much
9. wriggle out of my bag a little too much
10. decide to sleep with a make-shift hot water bottle
12. reposition/reloft/relocate the down in my bag
13. position myself appropriately on my mat, in my tent and environment (not in a valley that traps condensation etc.)....or not
...the shape of the toe-box becomes a moot point.... for me anyways.
Notwithstanding the importance of a properly fitted bag (which is why my last bag was customised from a wide 62" Zpacks bag down to 59"), I think some of the finer nuances such as the toe box configuration/profile become superfluous.
So I personally don't have a preference - however I most certainly respect the thoughts and preferences of others based on their own real world experiences and knowledge.
Edit: I'm only a size 10 US shoe, so not overly large feet...which most probably influences my opinion.