I have self-published my own manuscript on the same subject, titled, The Passion and Persuasion: A Deconstruction of the Evangelical Rhetoric of the Cross, wherein I address, in each chapter, respectively, the questions of justice, law, wrath, propitiation (along with redemption and reconciliation), and forgiveness, contrasting the traditional Evangelical doctrine of the atonement (i.e., as you say, the penal substitution theory, orginating with Anselm) with the biblical/covenantal understanding.

The bottom line, as I elaborate at length in my book, is that the God of legal justice (i.e., the Evangelical God) is incapable of forgiveness because forgiveness is, by definition, the cancellation of an unpaid debt whereas, according to the Evangelical doctrine, the law-God cancelled the so-called universal debt of sin only because it was paid by himSelf in the person of his Son (the so-called “second Person of the Godhead”).

Only by means of a covenantal understanding of the atonement can the seeming contradiction of forgiveness as the cancellation of an unpaid debt, on one hand, and Jesus death-as-payment (as per the metaphors of both propitiation and redemption), on the other, be resolved in a way that is satisfactory to a faith that is not at odds with reason.

A summary of and excerpt from my book can be read and, if you wish, a copy purchased from http://www.xlibris.com.

Again, good work on a subject in radical need of reexamination and clarification.

It seems much of this NPP debate has both sides throwing out the baby with the bathwater.