Very interesting idea. perhaps the separation of the soul and body is a process that takes a certain amount of time, and during this process the body could be revived, and the soul reinstated.
However, i think that if it's possible for people to literally will themselves to die, the soul would eventually leave the body if it was artificially kept in this state of limbo.
Willing themselves to die would be a conscious act, something not possible when you're in a vat of liquid nitrogen! But you raise another hypothesis that although the physical host is still viable, the soul may be linked to it via the conscious, thus if the conscious is disabled for long enough the soul departs.
I'm not sure it that's possible - people have been in vegatative states for years and come out just fine.
Maybe their soul vacated, but soemone else's moved in.
But hell, i've seen people who say the soul is never even bound in the body, and that they are completely separate. The only way to truly know how that sort of thing works would be a) undergo an actual "near death experience" or b) die. So who am i to say what happens, lol.
Not sure about the 'completely separate' part, otherwise I can't think of a reason why souls wouldn't play musical chairs with their physical hosts. Although maybe they do, but I'd like to think I'd notice.
My response would be, for one thing, that the soul is not exactly "in" the body to begin with. The soul is non-local--that is, nowhere in particular and everywhere at once.
The body is just the physical means that ther soul uses to manifest on the material plane, just as your TV set is the physical means that enables Jay Leno to be in your living room--Leno isn't exactly "in" the TV.
The soul may be non-local but the body isn't - one soul, one body.
My question is at what point, if any, would the soul permanently disassociate with its particular manifestion/host on this material plane, if the host were kept in a state of artificial preservation?