Karl, I’m glad you saw what I posted about Chinstrap, and I should’ve guessed you were aware of it.
I agree that splitting packages up into -devel, -headers, etc could be a good idea if you were going fully binary, but when you’re just installing a stack of GRP binaries to save some time, it’s a bad idea.
My USE flags are fairly close to the GRP ones, so what I often do is install all the packages I want, then:
emerge world –newuse -va
If I’m in a hurry, I just look for things missing that I care about and compile those.