It seems to me that the Hanged Man can also be seen as a kind of transitional figure. From the perspective of the one betrayed, he is a "condition of life". But if you take the card as being about what it depicts, namely the Hanged Man, he corresponds to a condition often depicted in association with Hell, which as you say was one of the four last things, the one you couldn't find depicted in the early "last trumps". Depictions of Hell in frescoes showed people hanged by one foot in Hell. This is possibly based on the Apocalypse of Peter, a non-heretical ancient Christian document which one source on the Internet (http://www.youall.com/HELL/dante.htm) thinks was also a source for some of Dante's imagery (my highlighting):Since the hanged man has nothing to do with “spiritual and celestial powers”, while “treason” is one of the accidents of human life, the Hanged Man belongs to the second group. But, indeed, if you cannot see meaning, you are left with only the evidence of the cards which didn't move in the different orderings.
The case with Death is different, because it is both the end of this life and the beginning of the after life. It belongs to both worlds.
Dante, I notice at that site, portrayed Simoniacs--clergy who sold sacramental favors--as upside down with their feet burning. That may be one thing alluded to by the Charles VI card, since the man is clutching money bags.And there were also others, women, hanged by their hair over that mire that bubbled up: and these were they who adorned themselves for adultery; and the men who mingled with them in the defilement of adultery, were hanging by the feet and their heads in that mire. And I said: I did not believe that I should come into this place.
Another possibility is that the Hanged Man represented, in Milan, Muzio Attendola Sforza, who had been depicted as a traitor by the anti-Pope John XXIII. This would have been seen by the Sforza family as an unjustified charge for a courageous action that helped to end the schism. In that case, shame is indeed simply an "accident of life" to be endured and overcome, as in fact the Sforza did. I see three signs of a positive interpretation of this card: first, his green legs, a color which elsewhere in the deck seems to connote fertility (the Empress and Batons courts). The hole (with perhaps water in it) underneath his head suggests the same thing, as a place to deposit a seed. And the wavy blond hair is like a halo around his head. However I don't see this interpretation fitting the cards of Florence.
If we describe the last part of the sequence as "increasing light" in a metaphorical as well as, in some cases, literal sense--it could also be described as "getting closer to God"--then the Hanged Man is at the bottom of that sequence, the one with no light, in Hell, the furthest from God. He is lower than the bottom of the Wheel, since all that happens there is a loss from fortune. Then Death is closer to God, in that at that point the soul at least is free from its earthly shell, the body. Then it meets the daemons in the air, the angels and demons that fight over the soul in various medieval depictions. Then it meets the purifying fire of Purgatory, at the end of which is Dante's Terrestrial Paradise, depicted, with its two streams, in the Star card (the stars being overhead, representing the strength of the light at that point and the hoped-for goal).
Here is an example of what I mean (upper part of an illumination for the manager of the Medici Bank in Geneva, later 15th century; the whole illumination is at http://2.bp.blogspot.com/-PRKkg1Y5dSk/U ... ssetti.JPG; Dante and Virgil are at the bottom, but it is not necessary, in a series of small images constructed for the viewer to put himself or herself in each scene, to put someone in the picture for the viewer to identify with)
In the PMB, however, the Star card merely represents the goal as seen from afar, the soul's longed-for union with God.. In the Charles VI it is the same, but as the Star of Bethlehem. Whether the extant PMB version is a replacement for a similar card in Milan is an unanswered question. As I say, the Bembo "Adoration of the Magi" of 1463 has such an image in its background. Also, it is unknown whether there was a Devil and Fire in the PMB. If they weren't there, it wouldn't matter to the interpretation.
Then it attains the Moon and the Sun, the most prominent of the celestials, the light increasing the closer to God it gets. In the visible universe, which is what we see on the Charles VI, the increasing light from Fire to Sun presages the greater light of the Angel and finally the World of the New Jerusalem.
After the sphere of the Fixed Stars, on the cosmograph, comes the "Crystalline Sphere" where the gate to the Empyrean is. That part may not have been illustrated in medieval times, I don't know. As I have said, the "hierarchy of light" may have been conceived in retrospect at a time when the Judgment card was already in place, as suggested by the fact that none of those before it are extant in the CY and the various early documents suggested 13-16 cards. Since in Christianity there is a Last Judgment before the maximum light, it logically goes there in any case. The final card admits one to the Empyrean, above the cosmos. In this life, this is a journey in imagination, an allegorical representation of life after death. But it is not a matter of just imagining oneself there, as one might imagine oneself in another country. It is a willed receptivity to images from another source, more "being taken on" than "taking" a journey, as in Dante, with one's intellect evaluating what one sees, even interacting with the images. I don't know how these things would have been done; I am mainly generalizing from Dante, although what I read there fits with other writings such as pseudo-Dionysius and the Chaldean Oracles.
This is the journey mainly from the perspective of the Cosmograph. For meaningful imagery of this allegorical journey, the Last Days are a valid and fruitful source; these images would have been recognized as part of the soul's journey in the sense of preparing the soul and allowing it to experience in imagination what it might thus be able to avoid in reality, an important function of art.
In this regard Death is omnipresent in the Last Days' depiction. The devils are for some reason not described as flying, unlike in Augustine and numerous other depictions. Nonetheless they are abundantly illustrated in Revelation images. There are also plenty of "acts of God"--lightning, hail, earthquakes, floods, you name it. The moon and the sun are there, too, recapitulating the Bethlehem story, then superseded by the light of the Lamb of the 2nd Coming, which unlike the sun and the moon shines both day and night. The New Jerusalem is also a fruitful image, especially in the case of the PMB.
The Last Days are a likely source of imagery and its associated moral and spritual lessons. But no Last Days narrative is structured in the way that the tarot sequence is structured. And card designers felt free not to use the Last Days theme if they wished something else, as in the case of much of the B and C imagery on the lower halves of the cards. The cosmograph gives the structure, as a metaphorical journey to God culminating in the Empyrean. The "increasing light" theme is there no matter what.
So about which of the various alternatives you posed at the beginning of the thread, Marco, my answer is: all of them except the de Mellet/de Gebelin. Of them, the "journey of the soul" and "cosmograph" determine the structure (along with the general theme of increasing light), and the Last Days, among other sources (such as depictions of Hell and Dante's Commedia) much of the imagery. That's at the beginning, i.e. up to the time when all 22 were there, whenever that was. Classical pagan sources may play a role in the imagery later on, or simply be additional interpretations, not necessary but helpful to some. That is a matter for further discussion, in relation to particular decks.
There remains the issue of how the Hanged Man and Death can be in two sections at once. I do not know if that is a problem or not; maybe "transitional cards" is enough. I'll try to revisit this theme.
Note: I added the visual the next day.