Hurtado cites serious scholars Nock and Hengel as both having shown how difficult it is to demonstrate that it is the application of pagan mythology onto Christ in Paul's writings that permits him to apply divine Sonship, Nock even concluding "[T]he attempts which have been made to explain it from the larger Hellenistic world will fail." (p. 103) (My emphasis. A. D. Nock, Early Christianity and its Hellenistic Background (New York: Harper and Row, 1964, p. 45). So if the divine sonship motif comes from within Judaism, how did that work? What did that mean? Paul's most exalted term for Jesus actually isn't "son of God", and in particular, it is absent at times when we might have seen it fitting to have used it (1 Corinthians chapters 8-10).
What is important to say from the first-century Roman era of Judaism is that the diversity of translations available to the Jewish communities of their Holy Scriptures would most certainly have included ideas of "sons of God", in particular with reference to the heavenly realm's population. But given the "failure" of this as the predominant ignition for the idea of Jesus' divine sonship, we need to look into Israel's sacred past. The most significant association, then, would most likely have been the ways in which God's anointed king of Israel (see esp. 2 Sam 7:14), other righteous individuals (some extra-biblical literature usage would have been well known) and Israel collectively (e.g., Exod. 4:22; Deut. 14:1; Isa. 1:2; Jer. 3:22; Hos. 1:10; 11:1; Wisd. of Sol. 12:21; 16:10, 26; 18:4, 13) as son(s) and "firstborn" of God. (p. 103). Given Paul's preference for other titles of Jesus with regards to the level of his exaltation, i.e. Kyrios (Lord), I think the most important allusion we should make here is that shared with the leading theme of the second gospel, Mark. The Jesus-God relationship represents the relationship God had always intended to maintain with his people collectively. Jesus powerfully represents "his" people. Whose people? It's now a double "his". God's people are now entrusted to their rightful king, the Messiah Jesus. In which case, although this is not a developed biblical speculation, there is also a double "son", the restored people of God as restored sons of God and Jesus as the archetypical Son.
Whatever the Pauline nuance usage behind his usage of the expression, I think the context shows that it was fairly far removed from the ways in which we can often hear it used today. As Hurtado himself points out (in agreement): In this messianic usage, divine sonship did not function to connote divinity, but it certainly indicated a special status and relationship to God.
So in summary: the divine sonship was a Jewish idea and Paul's occasional use of it in relationship to Jesus does not express his inherent divinity, but rather his unique standing and intimacy with God, and his involvement in God's redemptive work. (see p. 104) Regarding the fact that this took place in a social context where divine sonship meant something else, we can perhaps expect that this may have had an underscoring effect on the full ontological divination of Jesus as the serious theologizing and apologetics began to get into full swing in the subsequent centuries - part of a wider process I am calling triunification of God.