Balor brown is off. That conversion chart needs to be taken with a grain of salt, especially when it comes to looking at the new and old citadel paints. The citadel conversion chart itself is waaay off. I also own VMC brown sand and it too is off. I used to actually mix balor brown and XV-88 to get close to snakebite.
I think that Vallejo Game Color has almost direct conversions of Citadel's last paint line. If you look closely at the colors, for insranxe their dark flesh is exactly like the citadel dark flesh. Someone told me at my FLGS that the same company in China that made the last line of Citadel also made the VGC line. So they were made to be replacements for citadel paints. Anyway, true or not, I've seen several paints that match perfectly. My concern is with the snakebite leather, though. Max you are absolutely right that Cobra Leather is supposed to be the replacement. I have both the Vallego game color and game air version of this, and I've used both with success a number of times on my NMM gold. What has enticed me to ask here for SB is a post I put up on AndyG's WIP. He uses SB leather for his NMM gold, and I have been using the VGC replacement with decent results, but I can't help but notice his looks a bit more yellow. Then, on top of this, I read elsewhere from someone that used the cobra leather for their NMM gold that they, too, noticed that it seemed different from their snakebite leather.
In a nutshell, I know that Cobra Leather is a viable replacement, but I can't help but want to see this for myself and try out the Snakebite...