I am frequently in discussions (and not at all sure myself about the best choice) concerning the values embedded in the fairphone project and the need to maintain control about my personal information. In my view of modern society, these are both very very critical issues.
My choice so far has been for an open source software smartphone (first a Nokia N900, and now a jolla). Both of them worked really well for me.
As a consequence, it seems to me totally obvious that sailfish (the open source jolla OS), which is being ported to more and more recent smartphones and tablets, should be the primary OS for the fairphone.
I realize this may need some design choices for chipsets and things (or driver development), and I cannot judge how large these problems are.
But I repeat: nothing seems to me more obvious than this.