I'm using CIE DE2000, and when analyzing I often split it up to look at hue, lightness and chroma separately. It's not an exact measure though, especially in the more extreme ranges. When I was referring to a 3-4 DE difference it's just to indicate the scale of differences so which standard that is used doesn't matter that much.
The numbers included lightness, but I don't think "not correcting lightness + LUT relax" compared to "correcting lightness + LUT relax" does that much of a difference since the relax brings it closer to a matrix solution anyway, it depends on how strong relaxation is. All this can be controlled with DCamProf, and the default relax is quite strong.
The goals of a general-purpose profile and a reproduction profile is quite different. I aim for general-purpose profiles and then it doesn't make much sense to try to get colors super-correct for a particular target and lighting condition and introduce strong LUT stretches to do so. Instead the LUT is kept quite relaxed to guarantee good gradients in any condition, and then "the magic" takes place in applying the "film curve" and subtle subjective adjustments in the "look" (this is also applied via a LUT).
I'd love to put some more effort into the design bits and make a GUI etc, and I have still much to learn about this, but it's a huge project and you really can't sell the stuff in any numbers, so it's not strange that there's not much profile design software around... all stuff the manufacturers do is in-house with their own custom software, and they don't talk about how they do things.
Could you explain what you mean by "matching" cameras?
When you talk about DE, as you say you don't match lightness, is this effectively Delta AB?