Two-tier system?

In today’s Chronicle of Higher Education, Rob Jenkins suggests a “two-tier” approach to the future of the professoriate. Here is the link:

http://chronicle.com/article/Why-Not-a-2-Tier-System-/138521/

I think this is worth a conversation, but it raises a deeper question about the purpose of the PhD-track (top tier) faculty in his discussion. What *do* we add to our universities and cultures, to our classrooms and our conversations, for which our PhD educations provide unique qualification?

I personally would prefer one PhD track, and one “career,” but with the possibility of flexibility over that career. Not everyone, at all times, needs to be on the classic (but utterly false) 40/40/20 model. There are already numerous tracks, but we don’t understand them well, nor do our PhD programs adequately prepare future faculty for those varying opportunities.