Thank you for the link. A very interesting article. I had been thinking of something of a parallel approach, but was reluctant to raise it on FR because of my fear that it would reopen other, sometimes bitter, past FR disputes.
My approach is that the critical feature of our existence is our informed, free will which allows us to respond in faith to God's offer of redemption in Jesus Christ (or to reject same). The loss of that ability to exercise free will destroys our personhood, that is, the essence of our creation by God.
There are at least two conceptual problems, apart from measurement problems (Where is the situs of the will? How do we know when it is destroyed? Is it always yes or no or is there some continuum of destruction?), (i) what of those born without it who will never develop it? (Mental retardation) and (ii) what of Calvinists who posit no actual free will and eliminate the operation of the will entirely and (iii) is there a risk of 'eugenics'-type abuse in even discussing it. It was the Calvinist concern which caused me not to even raise my half-formed thoughts for fear of igniting a firestorm on tangential issues.
But your referenced article has started me thinking again. I have bookmarked it and shall read it a couple more times. Thanks again.