Another little update.
Note that I've been pretty busy with school stuff so that's why I've made so little progress, but here's a screenshot.
Smooth lighting! Its using the multi-lightmap with shaders idea and its working pretty well. Do note however this is just a modification my original test that I used to make the not-smooth-lighting screenshot from before, so extremely incomplete (note black block in hand), and has no semblance of an API. Just thought I'd post something so you know I haven't given it up.