The concept of Original Sin seems to beg for a nuance of firstness rather than uniqueness.

Why not both? When first, it is, until repeated, unique. In the biblical context, are we not faced with the conundrum of original independent thought equaling original sin? I've seen it argued that the biblical tale is an allegory for humankind's ceasing to be nomadic hunter-gatherers and settling down, raising crops "by the sweat of their brow," becoming husbands of animals (original meaning - nothing kinky implied!) and in that way, i.e. having gained the knowledge necessary to control their environment, they became slaves to the very environment they had mastered.

Now, as for Dub Dub's idea of creativity being original thought, I suspect that Joseph Campbell would have smiled on her idea, and would call the modern artist the equivalent of the ancient Shaman, reconnecting us to others and to the life of the spirit. It also fits with Mircea Eliade's concept of sacred time and profane time, the one circular, the other linear. Creativity exists as circular (sacred) time, but is performed in linear (profane) time.