I agree with you, except for the blame part.

Of course people act accordingly to the system they're in. If they expect punishment for an action, or not, changes their behaviour. By defining what's punishable, we can change the course of action. But if you look at any action which already happened, you can't blame anyone for it, because it had to happen that way, given the circumstances.

That already happened is key to your idea and I think you'd have got a better response if you included it initially. It's actually quite a worthwhile concept. Blame can't change the past. The important reason we blame is to help our mind cope with the loss we suffered. But if you can succeed in coping by thinking the past is immutable, that's even better.