It is striking that this passage interprets Jesus' death not as the outcome of his own faithfulness but as God's saving action. While this action has its own particular time and place, it is not closed in upon itself but forms the basis of the ongoing divine action in which God justifies the one who responds in faith. Faith, and consequently righteousness, is what is intended in God's action in the death of Jesus ... If, however, God's action in Christ intends the faith that leads to justification, this faith is itself the recognition and acknowledge of the divine saving action. In a two-way movement from Christ's death and back to it again, God's saving act in Christ seeks to elicit the answering faith that acknowledges it as what it truly is. Faith, then, is "faith of Jesus Christ" in the dual sense that Jesus Christ, the embodiment of God's saving action, is as such both the origin and the object of faith. In this way, the ambiugous gentiive formulations - "through faith of Jesus Christ", "the one who is of the faith of Jesus" (vv. 22, 26) - may be clarified, not by grammar but by context.
Francis Watson, Paul and the Hermeneutics of Faith (London: T&T Clark/Continuum, 2004), 75-76.
I confess that I am gradually being persuaded on the merits of the subjective genitive!