>> it's highly likely that "choice" is really a very complex chemical process, rather than some independent act that a unified person entity performs in complete isolation from their brain and body
I see this as a false dichotomy. It's the old mind/body duality again. Your assertion about chemicals is not wrong, but you'll run into trouble if you act as if it negates the subjective perspective.
If the subjective perspective is an illusion, an emergent behavior of a complex reality, then wouldn't we do better by trying to alter the reality (biochemistry and environment) directly than by abstractly influencing the illusion with notions of reward and punishment?
One of the interesting conclusions one can draw from studies of physics and biology is that it's highly likely that "choice" is really a very complex chemical process, rather than some independent act that a unified person entity performs in complete isolation from their brain and body.
Assuming for the sake of argument that this is completely true, I think we can make significant progress in improving people's ability to "choose" by approaching the problem of detrimental or criminal choices from a biological and physical perspective -- that is, to use a rational, scientific approach to influencing brains and bodies as highly complex, sentient physical objects, rather than a moral, philosophical approach to distributing punishment and reward.