Do you think the Jobian prologue/epilogue was an addition, as they seem to carry the same kind of language, encapsulating the prosaic body quite neatly?
If it is not a later addition, I guess the author is ironically using a naive folk story (Job being an old legendary character, along with Noah and Dan[i]el, in Ezekiel 14:14,20) to encapsulate his deep and corrosive poetic dialogue. But you must also take into account that a big part of the poetic dialogue itself is secondary (chapter 28 about Wisdom in the late mood of Proverbs 8--9, Elihu's discourse and Yhwh's second discourse at the very least). So it is very difficult to imagine how the author of the essential dialogues built his work in the first place.
Taking the line that the end result was rejection, surely that would then take him outside of the "family" and thus the covenantal blessings? Ergo if the original story ends badly, then it's potentially an example of what can happen to even the greatest of people, if they ultimately reject God?
Interestingly both the prosaic Prologue and the poetic dialogues (carefully avoiding the name Yhwh, with only one exception in 12:9) depict Job as a non-Israelite, out of any "covenant" relationship with God. Moreover, Wisdom literature in general is remarkably universalistic: the concepts of revelation and covenant play almost no part in it.
I personally tend to see the covenant theology (from Deuteronomism down to Calvinism) as one of the most perverse ever: any criticism is swept away because the critic puts him/herself out of the game and his/her protest is ipso facto invalid. How convenient.