Rick has written a very compelling piece on Reinin dichotomies here...http://socionist.blogspot.com/.
In addition, I think the same arguments can apply to "+/-"...and, I would say, to such dichotomies as "internal" (=N or F) and "external (=S or T).
Personally, I think that speculating about these dichotomies is a fun experimental exercise, and I'm always willing to explore even the most remote possibilities related to them (to the point that people sometimes wonder what on earth I'm thinking). I never tire of thinking that considering a new variant will lead to a new discovery.
But given the heavy discussion on derived dichotomies on this forum, and the degree of seriousness with which people take them, it's probably worthwhile to read this article.