Surely there exists reels from every time period of every film stock which includes SMPTE color bars? Or other color reference? Couldn't these be located from each (say) half-decade "era" and be corrected so as to establish a baseline correction for any other films on that stock of that age? I'm sure different storage conditions come into play on how the film ages but if you turn that correction into a plugin there can be sliders for "heat", "humidity", etc that change various parameters. Just a thought.