Stack comes with lts-2.9 resolver in stack.yaml. I know I already have a lot installed for lts-2.16 set of packages, and using this resolver would let me:

1. save disk space
2. save build time

Right now I had to edit stack.yaml, but what I'd like instead is to be able to do stack build --resolver lts-2.16.

As usual, if this seems like a good feature, I can put that on my queue and implement.