Katherine,
The Amarna example was one pulled from the top of my head. As with any analogy, it will break down when we examine it too closely. That, however, does not negate the concept behind the analogy.
It is important that I make myself clear: I am not speaking about modern interpretations of the texts and how those can change. I am speaking of the dynamic nature of the ancient Egyptian spiritual cosmology itself and how
it changed over the centuries. Certain elements did remain relatively static (i.e., the concept of the Primeval Mound; the basic cosmography of Nun, Nut, Geb, Shu, Waterway, etc; and as you've pointed out, the concept of Seth as representative of "foreigners") but that does not mean that every element, especially those with a record of change, were immediately made stagnant and constant before Dynasty VI.
To backdate dynamic texts into a cultural era for which no evidence supports its existence (or at least its prevalence) is a mistake that can easily lead researchers away from the real beliefs of said culture at the time period in question.
Anthony
You can lead a horse to water but you can't make him think.