versioning non-Python runtimes

I'm investigating upgrading nodejs (https://github.com/conda-forge/nodejs-feedstock/pull/6) to 6, but ran into the fact that downstream packages really need to be tied to at least the major, and probably minor, version of node, so issuing the upgrade would likely break all downstream packages. The same likely goes for any non-Python runtime, including R (most used on conda), ruby, etc.

So my questions are:
1. what's in-scope for conda-forge (matrix builds of nodejs versions, ruby versions, etc. like CI services have?)
2. what's in-scope for conda itself (a generic mechanism analogous to CONDA_PY?)
3. how do we specify which nodejs version for a package (track features, or just pin the minor version in recipe.yml?)

I think the general question brought up elsewhere of pinning versions of dependencies at build-time would also ease this issue.