About 1.: I considered that but from the few grep I did it seemed that I would have has to modify other import plugins to take that into account (most don't seem to collect settings from command/init.py)

Which besides hitting hard on my lazyness :) also led me to think that it could also break plugins that are not in the repo and didn't explicitely set this variable in the template context.

And as I don't know how far goes the compatibility constraints for nikola minor versions, I went for the most minimal (in terms of code and possible side-effect) change.

I'm still open to offer a hand on the other options, but it's really not up to me to tell if it's worth it.