So I'm building a portal map that has, as a theme, the possibility of certain areas losing power (and power being restored to those areas).

As part of this, I've de/recompiled a LOT of the models to make non-glowy versions, took one of the lights from props_c17 (HL2 I know, but I think it's available in Portal to someone w/o HL2) and made a version that can be turned on/off, and lots of other things.

I like the recessed lighting used on most of the real maps, but unfortunately there's no way to toggle texlights on/off so that's not an option. So I'm forced to come up with my own lights...

I think my 'emergency lights' turned out good (this is what my first test run with them looked like, I haven't changed them at all since except for placement), but I'm having trouble getting the general lighting right. Any suggestions?

Lit version. Note active portal cleanser and glow

Dark version. Note portal cleanser off and no longer glowing. (Ignore the switch, it's for testing only. The fact that the switch glows like it does is why I reskinned everything...)

Can't you use a toggling brush with the "block light" texture to cover up the recessed lighting or any other light-emitting textures?

Yes that would likely work, however it would leave a very ugly line where the light stops.

Can't you use a env_screenoverlay or a color_correction?
I mean, not actually modifying the source of the lights, but simultanously add new lights to the actual scene that is actually brighter or distinct from the regular light sources so you use the HSV functionnality of the colorcorrection UI to fake a blackout.