I hesitate to enter this discussion b/c I probably won’t have time to engage thoroughly. But I wanted to add some thoughts:
Dual authorship and authorial intent are not necessarily competing options.
Divine authorial intent should be seen as organically related to human authorial intent, though the former may take a direction that would’ve surprised (but not ultimately undermined) the human author. For example, if Ezekiel were transported into the NT era to hear the apostolic interpretation of his prophecies, he’d say, “Wow, I didn’t see that coming. But, come to think of it, I can now see how it all fits together given the Christ event and greater clarifying revelation. In the end, this is what I was saying ‘though a glass darkly.’” My main concern is if we envision a divine intent that is wholly unrelated (let alone contradictory) to the human intent.
The identity of “human author” and “audience” is complex. Take Psalms as the first example. Is the “authorial intent” of a specific psalm derived from the poet himself or the editors of the Psalter (who lived in the postexilic community)? Much work has been done on the editorial process of the book: the five “books”; the order and arrangement of the psalms overall; seeing Pss 1-2 as an introduction to the whole (and Pss 146-150 as its conclusion); etc. The end result is a clever,
intentionally arranged “book” that adds potency and an eschatological messianic angle not necessarily envisioned by the individual poet of a given psalm. In fact, the overtly eschatological thrust of the entire book fits the NT appropriation of Christ (and the church) as the ultimate fulfillment of the Psalms.
Proverbs is another example. The vast majority of the book comes across as the psalms of Solomon. But there are post-Solomonic additions and arrangement to achieve the book as we have it. It is not a collection of random sayings, but a real “book” with an overall intent, thus put together for an audience different from the original (i.e., “my son”). I’d suggest that the final intent challenges encroaching Greek philosophy/wisdom not in the original orbit of Solomon.
With both, we really need to think of Implied Author and Implied Audience–the latter encompassing the People of God that transcends a apecific generation (and the broadening of the audience is intentional by the editors). I’d suggest the same for much of, if not all, the OT books. It’s a bit different in the NT, since these books were put together relatively quickly and within the same generation (or so). Though there is some parallel in the Gospels. As they quote Jesus (an author of his words), they shape and rework both the words themselves and where they fit into the arrangement of a given Gospel. So is authorial intent “what Jesus said” or “what Matthew (e.g.) meant by shaping and arranging it here.”
I probably have more thoughts, but I’ll let others to see if this is a help or a distraction. Again, I can’t promise immediate engagement.