Inspiration is itself a model of imitation, or a particularly complicated singular rhythym of imitation, in which the composer, or prophet in this case, imitates the model of responsiveness itself. I've done a little work in rhetorics of the shaman, but a prophetic writer, while operating in a different religio-cultural context, could be argued to operate in composition, oral or written, in a similar fashion. Don't quote, that's a chapter yet to be written.
The reality of composed document in itself has no bearing on its being an imitation and/or creation, invention, or given, as both modes of textual production operate with simultaneity, whether linguistically, thematically, or consciously.
I'm doing a lot of ground work in imitation in classical sense, specificially in the areas of rhetroical theory and pedagogy, of which they concieved of imitation as a crucial part. The concept of imitation also is the root in representation of moral models to follow. If folks wish to be Christ-like, it is a set of lives and actions in imitation of that particular figure.
I completely agree that historicization is crucial in any theoretical invesitgation of text or textual production, but I think that as long as that is acknowledged, as well as the influences of predecessors, like Mediveal monastic scholar's influenced by neo-Platonic scholars through figures like Aquinas, and developments beginning that will be manifest more overtly later, the application of theory to texts written before theory was codified can be very productive.