Does the metaphor of the olive tree (Romans 11:17-24) undermine the notion of Jewish distinctiveness in Paul’s thought?

In my book, I argue that:
Paul and the Vocation of Israel: How Paul's Jewish Identity Informs his Apostolic Ministry, with Special Reference to Romans

In light of the gospel, Paul sees an ongoing, distinct and positive value for Jewish identity, even within the Christian communities … Paul is convinced that God’s revelation to Israel provides Israel with a special role or task within God’s wider purposes—a divine vocation. (p. 20)

Romans 11:17-24 is often seen as a challenge to this notion of Jewish distinctiveness:

A number of interpreters regard Paul’s metaphor of the olive tree in Rom 11:17–24 as evidence that Paul is seeking to include Gentiles within a redefined Israel. (p. 51)

However, I contend that:

Paul is using the olive tree metaphor neither to claim that the Gentiles are joining Israel itself, nor to eradicate Israel’s ethnic distinctiveness. Rather, Paul is using the metaphor to describe the relationship between Israel and Christ-believing Gentiles: both share in the same root (God and / or the patriarchs), but Israel is more “naturally” related to this root than the Gentiles are, even if there has been a temporary “breaking off” because of unbelief. This description serves Paul’s stated purpose to quell Gentile pride (Rom 11:18). However, it is not intended to imply that the Gentiles are now to be regarded as members of Israel. (pp. 52-53)

The details of the argument and further references may be found in chapter 3 of the book. The chapter is available from the publisher in electronic format:

Windsor, Lionel J. Paul and the Vocation of Israel: How Paul’s Jewish Identity Informs his Apostolic Ministry, with Special Reference to Romans. BZNW 205. Berlin / Boston: Walter de Gruyter, 2014.