I have a feeling that history will not be enamoured too much with Downes meddling. His Buckfast creation is now gone and his influence on the organs in the RFH, Gloucester and St Albans cathedrals has all but dissolved.
I have some difficulty with the term 'meddling' being applied to Downes's work. Views about organ advisers naturally vary widely, but he worked at a time when several (if not many) of his peers were not musicians at all - Cecil Clutton was an example, who could barely play a note. I have seen him described as "a boorish and independently wealthy dilettante with too much free time whose disproportionate influence and lack of social graces bore scant correlation to his actual talents". This too might be unfair, and it's a view which is unlikely to be universally shared, but it confirms that we all probably have our own favourites among both past and present members of the breed. Clutton's close buddy and another amateur, George Dixon, dismissed in print the sound of the instruments Bach played as "sausage frying". That sort of thing is not organ consultancy.
Looking at him objectively, Downes was highly qualified and experienced as a musician (unlike those just mentioned) and he also did a great deal of research to support his consultancy interests. Even today one can still learn much from his book 'Baroque Tricks' about the scaling, voicing and other organ building practices of great 17th and 18th century European organ builders. It is a testament to his dedication that he was able to discover so much about their work while the Cold War was at its height, with access to some instruments, and indeed to much scholarship, being so difficult.
So I would not say he was a mere meddler. His legacy is bound to be viewed differently today, if only because we are all experts with the advantage of 20/20 hindsight. But I venture to suggest that many will still pause to consider what he did carefully before forming a judgement.