A shame none of the Vimeo footage is viewable anymore. I’d love to see what progress was made at the time.
Although I doubt this is a useful bit or anything since probably someone else is covering this base on your team of restorators, I believe that this movie will be easier to fix the mild fading issue than most others for the basic fact that it provides hard captions as well as much of the footage being hard matted. Theoretically, one can make a white balance using the hard matte as an obvious black point and the captions as a white point.
I made a little test real fast to demonstrate my point (although please note, I forgot the title was “Return” not “Revenge” so minor whoops lol): http://screenshotcomparison.com/comparison/132337
I must say, I am really impressed by what I am seeing, especially considering the fact that I was honestly expecting this to never come to actual fruition. Unfortunately, I cannot provide any real help though as much as I wish to, though I will give some minor tips if I think of anything useful, although you pretty much have your priorities straight for the most part and I can appreciate the no DNR aspect as well as the implementation of the original theatrical mix (though I hope it’ll be noise reduced, but if not, I’m sure someone can do that easily enough; not that I’m expert on any of that really though, so sorry). The only thing I can really say is that I recommend trying to refrain from screwing with the colors as much as possible to retain the theatrically intended color scheme (rather than trying to create a “clean, natural” look). I would recommend trying to simply reduce the fading and leave it at that.
As I said before, I wish I can say that I can be of help, especially as a fan who’s seen nearly every Godzilla movie out there–with this being one of the few exceptions–but sadly, I have no skills in any of these departments really nor any spare cash currently.