The original stock shots look the way they do because the original film elements were damaged from use and re-use. They're not going to look any better, which is the reason for the new effects in the first place.
If we can put a man on the moon, we can digitally clean up some film from 1966.
One thing I COULD go for -- and this could get me kicked out of the reactionary club -- using some original "real" footage: standardize the Enterprise's phaser/torpedo effects.