While I'm happy to see you reading Zahnd, I think the scapegoating angle is a stretch.

The frame of the woman caught in adultery is about how Jesus reacts to mosaic law, a theme we see consistently in Jesus interactions with the Pharisees such as over divorce, the sabbath and forgiveness of sins.

If the opposition of enforcement of law here is really about scapegoating and Jesus is opposed not just to the situation but the entire practice in general, then he plays into the Pharisees hands and opposes the mosaic (divine) law as unjust on principle. Exposing himself not only as a perverter of Justice (read Righteousness, the two are synonymous) but also a blasphemer.

Yet at no point in the story does Jesus condemn the practice nor oppose capital punishment itself (Paul writes that such can be an instrument of divine wrath in action as final consequence of sin). It is not the law itself, but the people who enact the law in such a way as to pervert it to be unjust that Jesus opposes, again a common theme in his ministry.

Keep in mind were the intent of the author to highlight the issue with the law itself, then the story could show the innocently wrongly accused. Yet the story we find in John goes to great lengths to point out this woman is guilty of her crimes. There are witnesses, this is not the woman accused of adultery, but the woman caught in adultery.

It can only be Scapegoating if the goat is an innocent party, which this woman is clearly not. Jesus not only doesn't challenge the accusations of her guilt, but openly acknowledges it "go and sin no more".

While I do feel you have some valid and great points with regards scapegoating and atonement, my own opinion disagrees strongly with the line:

Jesus has just freed a sacrificial victim and exposed the scapegoat mechanism as a fraud - and afterwards he said that he judges no one.

There was no sacrifical victim, or if we see her in the light of a poor sinner caught in the web of a broken, brutal and injust legal system, then Barabbas must be considered in the same manner and the crowds choosing of him over Jesus is actually their merciful release of a "sacrificial victim". I'm not seeing that personally.

I also find the notion Jesus "doesn't judge" to be odd considering John 8 is bracketed by chapters in which Jesus says both "Do not judge by appearances, but judge with right judgment” and "I came into this world for judgment so that those who do not see may see".

Not casting the first stone isn't about abandoning judgment entirely, but doing so with the moral priority focused on an understanding of the accused that seeks restoration of community (and creation) rather than condemnation and isolation.

I've recommended the book a few times but I really think you'd enjoy Beyond Retribution by Christopher Marshall, which examines the prevailing interpretation of biblical justice and seeks to promote restorative justice over retributive justice interpretations.