OK, I made a test using two clips from Mondo and 4K BDs, of the same scene of the last screenshots posted here (thanks to doombot).
During the comparisons between 4K and Mondo (magnified from 4x up to 8x) I noted a strange thing: sometimes the 4K has less details in part of the image, while more in another... sort of out of focus... plus, in a shot, the image "moves" up, down, left and right a lot more than Mondo, where the image is not perfectly steady, but with much less "movement"... add to this the fact that Mondo has few frames more - like 4 out of 1000, not so much, OK, and they are frames at the beginning and/or ending of a shot, but if it's the same for the whole movie, summed up we are talking of almost one MINUTE lost!!!
Regrading results: not too bad, but not perfect either; in some shots the color grading matches almost perfectly the Mondo, while in others there are visible artefacts, "thanks" to the ColourMatch script that is "stupid" and doesn't cope well with different cropping between the two versions... at the end, I'm not happy with it as it is now; it needs a lot of further testing and subsequential adjustements that frankly I don't know if I'll be able to achieve.
Then, I had a stroke of genius... my brain said: "Because we want the Mondo BD color grading, but the 4K BD seems to have a better resolution, what if..."
As the Mondo has a quite good resolution, IMHO only ruined partially by compression artefacts and lack of fine grain, I thought to "enhance" it a bit, then "slap" a grain plate on top of it... result? Take a look and let me know what do you think:
Mondo BD Vs Mondo BD enhanced +grain plate applied (from compressed file @30mbps)
http://screenshotcomparison.com/comparison/78813
Am I completely fool?!? Waiting for you pro or cons feedbacks!
If you want to watch the clips (Mondo BD "as is" and Mondo BD enhanced +grain plate applied), let me know and I'll post the links here.