Thanks for the link, although no solution is in sight . In my opinion, however, one aspect is missing, namely that most cameras are ISO-variant. In low-light photography there is an optimum iso-setting, with the best S/N ratio. See this link: How to Find the Best ISO.
DP Review had another article published a long time ago about ISO variant and invariant cameras, and I remember reading a lot of back and forth/bickering about how ISO is not gain but only mapping of brightness values. There is also hardware ISO and software ISO and manufacturers are known to mix them as well.
I will add here that Magic Lantern offers raw histograms for (some) Canon DSLRs, though my brief flirtation with them concluded that the histogram is too small and brief for me to understand much I have also heard discussions about how ETTR destroys skin tones though I am yet to verify this for myself.