Although I agree that preserving 35 mm prints is very much worthwhile, and I believe home video releases should preferably have a color grading that echoes the theatrical experience, I do not completely agree with your last point. A print scan on a small screen does not reflect what is seen on the big screen. The color depth of a home release is much less, so things that in the darkness that can be easily seen in a theatre would disappear into blackness on a small screen. This is why home video color grading does have it’s purpose. So, although it is fun to watch a print scan on the small screen, I would not consider it the ultimate home movie experience.
You ask the question, what’s the correct contrast for the sky in Ghostbusters? I would say until our small screens are able to reflect the color depth of the big screen it is a matter of debate.
This just depends on how the preserver does the mapping when reducing the color space, contrast and black levels from the scan to the final format (a rendering intent of sorts). Personally I would trust the people here to do a better (read more accurate to the original theatrical version or whatever version happens to be the target) job than the makers of the home video releases. They are typically balanced toward the speed and profit side of the scale these days it seems.
Not that the job isn’t adequate in most cases, but when you really want to watch a special version of a film on a calibrated display in a light controlled room, this is a good place to visit to get that history and nostalgia.