Hey Neuro,
I'm curious as to how Harry's death in Changes fits into the theory. Mortal free will is important, according to the theory- except Harry's death was a result of a compromised Free Will, and neither Uriel nor Mab moved or acted to stop it, despite their intelligence level/foresight. I can understand Uriel not being able to act to prevent it, given that he may not be able to act unless his opponent breaks a rule, but Harry had to answer Mab when she asked him about partaking of the death angel, as she put it, to get out of another deal with her (per Changes). Per your theory, wouldn't she have acted, in some way shape or form, to prevent him from taking his own life even though he gave his word that he wouldn't?
Also, the presence of the parasite within Harry for as long as it was there poses some issues. With it perpetually feeding off of Harry (and, presumably, any / all powerups he received during the time frame in which it was present), coupled with its ability to nearly incapacitate him with headaches (as we see during the opening chapters of SG), you have a really good recipe for a permanently dead starborn swiss army/utility knife.