In the draft list for the Western tradition, I have included Solovyov's work Lectures on Humanity. By most counts, Solovyov was a creative religious thinker - he started modern Russian Christian thought on Sophia ("Sophiology"), was an accomplished philosopher and mystical poet, and was held in high regards by Catholic theologian Hans Ur von Balthasar.
I have read Lectures on Humanity recently, and after reading it I was truly at a loss as to whether this should take a spot in the list. It's theology is in fact quite traditional. And while it mentions Sophiology - its treatment was not quite superficial (not a focus of the lectures. In its discussions about other religious traditions (the first half), it was not particularly interesting. In the cultural strategy it laid out (something along the line that the future Divine Humanity is to be accomplished in history through combining Russian preservation of the Divine side and Western development on the Human side) was not historically significant.
There are two potential ways to replace this - either by another of Solovyov's work; or replace Solovyov's work with Dostoyevsky's Brothers Karamazov. Either way there would be one less text in Orthodox Christian tradition and one more text in the Slavic tradition in my latest thinking of Western sub-traditions (which btw seems a bit artificial from this example!).
Not decided yet.