…I still find that when the question is one of vindication, Paul points
straight back to the cross-and-resurrection.

Yes, at times Paul looks back (1 Cor. 15:17), but he also (and I think more
characteristically) looks forwards to an event that will vindicate both him and his churches for the faithful stance that they have taken in the face of opposition. So for example, when he is
talking about the need for the Philippians to endure suffering, he urges them to
hold fast to the word of life, ‘so that in the day of Christ I may be proud that I did not run in vain or labor in
vain’ (Phil. 2:16). It will be part of his vindication that he has built
communities that will survive persecution. Similarly, in chapter three he speaks
of suffering with Christ in order to share in his resurrection and be
transformed at the appearing of the Christ (3:10-21). The Thessalonians suffer
extreme affliction but they will be vindicated and glorified when Jesus is
revealed from heaven (2 Thess. 1:4-10).

I would say that the point of the ‘in Christ’ statements is basically that the
early church is participating in his story, which is a story of suffering,
resurrection and a coming vindication at the parousia. The churches of
the Greek-Roman world are included in ‘way’ of Jesus - they are the
radical Jesus movement, because they experience the same extreme hostility when
they announce the imminent arrival of the kingdom of God. That’s what Jesus and
Paul stand for. What defines us, however, I would argue, is something different:
the calling to be God’s new creation people as it has been reshaped by the
redemptive events of the New Testament story.