it seems to me that any 'tweaking' is a matter of taste and preference of the editor in charge of creating the new release. I think this is particular true with the color [timing?] -- a little out of my element here ... lol.
My cautious point (I am on very shakey ground with respect to the technicalities here) is that I don't know what you expect to hear and see in a third blu-ray release of 'Zulu'.
Having two versions to compare makes this easier to answer, i could see clearly that the UK version had DNR and contrast boosting that removed detail, you could also see clearly edge enhancement halo's on the TT version, neither version is great, i rented the UK version and thought it abyssmal and i bought the TT version and until a better one comes along i will keep it.
There is another version out there released by Inspired Pictures in the USA that obviously uses the UK master but does not have the over saturated colours, go to Cap-A-Holics if you wish to view some caps from it.
For a third blu ray release, i'd want a modern new 4K film scan, the TT audio, no over saturation of colours, no contrast boost and especially no excessive edge enhancement or DNR applied, that would make me very happy, i'd pay a lot for that version.
P.S. I hope this doesn't start the arguments up again, this is just my opinion on both these releases.