You will have a completely "dark" level when setting
the unlit flag on the level-block-models.
You dont needs any BSP then.

then also set the light flag on the entites,
give them a color, and
adjust their material values.

This way you have complete control of the lightrendering
of the model entities.
Also set sun_light =0; to eliminate the dynamic sunlight.

Some small recent games of mine:
Griefer 4k http://damocles11.byethost9.com/griefer4k.html
Kobold 4k http://damocles11.byethost9.com/kobold.html
Cave 4k http://damocles11.byethost9.com/cave4k.html