Here's what comes to mind for me, at least, when I hear the terms light or dark.
Darkest:
- consonant clusters
- voiced sounds
- nasals and stops
- place of articulation in the back of the mouth
- consonantal nuclei (l, r , m, n)
Lightest:
- (C)V structure
- unvoiced sounds
- approximates
- articulated closer to the front of the mouth
I'd be curious how BWR's definitions compare, because 'light' and 'dark' aren't exactly clearly defined.
This converter is a pretty useful tool. If you don't know x-sampa, just remember that to superscript something, put an underscore before it.
I'm low on time now, so I can't say much on the bulk of your post, but it looked pretty cool and well thought out from what I saw. If we do decide consonant clusters are something central to a dark sound, those would probably make up the roots and the different stress levels would cause certain sounds to elide. Or something.