I agree with all you said. My comments throughout are directed entirely to non-staining developers. I feel that you can get results as good with 2 developing agents though and that adding a third is, to an extent, redundant based solely on comments by Haist and based on his work, that of Henn and also Lee.

Sulfite merely adds to the overall equation by sopping up the quinone and regenerating a milder developing agent and putting it back into the pool of avialble developing agent.

The ratio of activity of HQ to HQ-monosulfonate is about 1:25 or larger.

Keith, mercaptans tend to be silver halide solvents and at the same time can act as such while lowering or eliminating the tendancy to form dichroic fog. I'm not sure of the cinnamic acid though unless it is there to mask the odor of the mercaptan. Cinnamic acid smells rather nice IIRC, even as a salt, but generally mercaptans stink. Oil of skunk is t-butyl mercaptan BTW just to put it in perspective.