Some humble thoughts of mine: http://www.imperial-library.info/fsg/nalionarticle2.shtml
I was reading this, and I came across your recounting of the KotN prophet's words:
"Are there no ears to hear the warnings? Are there no eyes to witness the Wheel's breaking? The Eight and One favor only the righteous! And too few of you remain! The Thief has found the lock that he cannot break! The Warrior, the foe that cannot fall! The Wizard, an incantation that takes not to his tongue!
Truly this is the Age of the Serpent and the Void that follows!
The Guardians have fallen and no one remains to watch their charges, and all the heavens are now banquet for the Princes of Misrule!"
Now, I just spent some time modding the birthsigns for Morrowind, and what the prophet says reminds me strongly of the signs.
Additonally, Vivec seems to talk about the Signs, too:
"And it was of the Tower that my emperor wanted to hear. He was dying and I loved him yet. He, too, was a Master and so I knew that he realized just how big a realm that the Tower encompassed. I am sure that when I meet the Warrior and Arctus again, they will have brought similar burdens. My guesses are the Lord and Ritual, but I do not know and would be delighted to be wrong."
I refer you then to http://www.imperial-library.info/obbooks/ffoulke_firmament.shtml. The Warrior, Thief, and the Mage (Wizard) each have their charges.
Warrior: Lady, Steed, Lord
Thief: Lover, Shadow, Tower
Mage: Apprentice, Golem (the Atronach), Ritual
In the CS, the Thief Birthsign is referred to as "Hara." Perhaps she is the original NIRN Thief Guardian?
At any rate... I'm not sure where I was going with this... Right. So, perhaps the birthsigns mimic the roles of the Guardians?
Oh, yes, and the Serpent:
Serpent wanders about in the sky and has no Season, though its motions are predictable to a degree. No characteristics are common to all who are born under the sign of the Serpent. Those born under this sign are the most blessed and the most cursed.
Perhaps the Lords of Misrule, or their representative? As the Prophet said, "Truly this is the Age of
the Serpent and the Void that follows!" Where the Void is... Oblivion?
Now, I'm a bit confused as to why the creation model follows a wheel. Does it have to do with the original 8 Aedra that became the Earthbones? And if the tower is the center.... with Lorkhan as the 9th (Talos' enantiomorph) and the center... hmm.... not sure where I was going with that though.
It is interesting what you say here:
A question that arises is wether Red Tower could have fallen without the fall of its Guardians? Reconsidering the situation of Red Tower at the time of the Nerevarine, the Tribunal still held a weak grip on Red Tower, they still acted as Guardians, but Dagoth Ur was on the rise. Eventually he would have won. If Dagoth Ur had won, the Tribunal would have been gone, but it also would have created another Guardian, whether willingly or not, a Guardian named Dagoth Ur with a walking copy of Numidium. A copy of Walk-Brass - powered by the very heartstone of Red Tower, in the hands of Dagoth Ur who wasn't friends with the Daedra either. While knowing that interpreting a Daedric Prince's actions and motives is a risky business at best, in this case, one assumption can be made: If the Daedra wanted the barriers to fall, Red Tower would have to fall. To accomplish this, they would have needed to elimiate the protection of the Tribunal while at the same time stopping Dagoth Ur from fulfilling his goal and completing Akulakhan. At this stage, the Nerevarine entered the stage with the outcome we are familiar with. The Tribunal severed from the heart and broken, with Sotha Sil and Almalexia dead. Dagoth Ur was defeated. For the Daedra? The event killed two birds with one stone.
It really seems like Azura is a manipulative little rat; two birds with one stone, one step closer to gobbling up the creatia of the Mundus.
Walk-Brass is a golem.... the Atronach sign is also referred to as the Golem. Is there mimicry/parallelism/whatever here, too?
I'm kinda new to lore-ness, so I could be interpreting things crazy.