Nice article. I'm pleased it got the implications of Charlemagne's coronation as Emperor more or less right, by acknowledging the legal status of the Emperor in Constantinople.
I should relate, however, the view expressed by the late H. Tristram Englehardt (raised Southern Baptist, converted to Holy Orthodoxy late in life, simultaneously held in bioethics at both Baylor's med school and Rice's Dept. of Philosophy): in a discussion of what has gone wrong with the world, and the cultural decline of the West, someone ask in his presence, "When did it all start to go wrong?" Engelhardt' replied, "Let me see, if I recall correctly it was just after the third Mass of Christmas in the year 800..."
A lot of us Orthodox Christians see the attempt to revive the office of Western Augustus and the resulting existence of a competing "Holy" Roman Empire under the patronage of the still-Orthodox Popes of Rome as the foundation of what eventually became the schism of Rome from the Church (yes, unless you accept the papal claims, which we never have, that's what happened two and a half centuries later), the rise of rationalism in the West (Aquinas was actually a precursor of the later rationalists, who had less regard for Scripture and Holy Tradition) and inevitably of secularism and unbelief.