The /etc/portage/env hack is very nice, and as a maintainer of several binhosts, I've been waiting desperately for that feature. However really useful things like FEATURES="-buildpkg" still can't be done with it. I suppose this requires some restructuring in portage's config handling.
Steps to Reproduce:
This seems to depend on proper implementation of bug #44796, comment #50, but I'm not sure...
*** This bug has been marked as a duplicate of bug 44796 ***