"I believe that the Armenians (who are Eastern, but not Orthodox) may observe the Nativity on January 6th rather than Theophany, but this is a bit fuzzy in my memory."
Your memory isn't as fuzzy as you thought. The Armenians are the only ones, and it is an ancient, ancient tradition.
Your comments on the possible convergence of the Feast of the Annunciation and Great Friday point up a major mindset difference between the Church in the West and the Church in the East. While the Passion surely is important in Orthodoxy, nevertheless, the Incarnation which allows Man to become divinized as God took on human form, and the descent into Hell and Resurrection whereby the power of death and the Evil One were overthrown as so magnificently expressed by St. John Chrysostomos speak to a rather different concept of salvation in the East from that in the West.
Well, that's always nice to know. I needed that today! :-)