Kix, thank you for the interesting idea.

I think indirect GI can be used for different types of highlights in many scenarios. The lights with different specular and diffuse settings are usually used to simmulate indirect lighting/bounce lights, so they are used to avoid the render time expense of the indirect lighting calculations.

But I think your method is wonderful for what I've been describing above -- about the modeled sky dome. I just tested it and it gives very good results: I can set the same map to the glow channel, as I do to the sky dome color, I can use the ShaderPlus plug in to set the sky dome's shader not to receive any lighting or shadowing itself (and thus cut down the render time a bit) and I can render with indirect lighting only (no need for sky lighting) in the GI section upped to about 250% for a very realistic effect of the sky light emmited by my skydome. (No need to increase the glow value in the shader even, just an incrased indirect lighting effect). On pretty decent quality settings the render time is a bit expensive -- 1:15 minutes for my very simple scene (1 sphere, 1 plane, 1 sky dome hemisphere, no other lights whatsoever), but it does give a nice result, where something like this is needed.