You'll also need to spend time getting the two sets of data to overlap, which will probably mean registering and changing the geometry of the images (I believe OCP had to apply lens distortions to make his editions).
Since colour resolution doesn't need to be as high as luminance, maybe you get a decent result.
Maybe you do, but the real problem with composite video is the chroma signal. If anything needs to be replaced, it's that. I really doubt that a new luma channel is going to make much of a difference.
DE