Its also possible to roto around some of the additions, like the rontos. Adywan did this with the most major, most invasive enhancement--the foreground ronto during the "these aren't the droids you're looking for anymore." I think Adywan said it was the hardest thing he had to do to de-SE the film. There's a lot of background rontos that would be more easily rotoscoped out using a GOUT comp that should be about as noticeable as the cloud city rotos in ESB. The hard parts are restoring the OOT-only shots, like the entry into Mos Eisley, the establishing shot of Ben's hovel, and the original X-wing shots. The quality would probably be noticeable. Then there are other shots like the establishing shot of the moisture farm, which might be left as the SE enhancement since it's so minor, or perhaps cropped to the original framing, although you could roto out the extra vaporators if you were feeling ambitious.
It would be possible to do ANH in the same as ESB, it would just be a hell of a lot more work. But one of my main problems is that the contrast and sharpness would still be there. ANH was photographed gauzy, and I think it would just look weird if you put a soft filter on in photoshop. ESB you get away with the SE sharpness because the sharpening was very minor, and it was always contrasty too, but ANH is a different beast altogether. I would be more interested in finding some way to use the GOUT and somehow layer in detail levels from the SE using photoshop or something, but I'm not sure if this is even possible. I know X/0 was doing something similar using Black Magic.