> Given the limited materials that Lego bricks are made out of, getting sensible default materials and automated lighting would be hella easy.

So, don't wast time and give us your pull request! ;-)

https://github.com/leozide/leocad/pulls

Other option is use Blender with "ImportLDraw" addon for import and render models produced with LeoCAD

https://github.com/TobyLobster/ImportLDraw

Combination of LeoCAD for modelling & Blender (Cycles Render) for rendering - really COOL thing!