Hal,
If I am following your post correctly, you would suggest a compromise, where work requiring some level of consciousness would be accomplished by a subset of a posthuman's mind, which could be distributed over several different physical localities and focused on many different tasks simultaneously. This way we would have the advantage of special purpose consciousness dedicated to tasks but with a greater life beyond the workaday world through its intimate connection as a part of the general purpose posthuman mind. This is an idea that I have thought of myself as being one way around the ethical dilemma of special purpose sentients. Thank you for raising the concept in relation to the question I proposed. Borganism labor instead of slave labor?
Glen Finney