I have written columns about some of these subjects and at some point would like to put some stuff I have learned and researched online, maybe you would be interested in being that vehicle since you have already spoken some of the topics described...
However, where I disagree and want to give you some food for thought is you seem to imply that "legitimate credentials" of black belts/instructors got their dan grades "in person" from "an organization that they trained in.” Then you made a point about video exams being of less credibility.
I personally feel that "ALL black belts" to be "credible" should have trained with a "real school" (not from a video tape) and got their black belt "in person" from an instructor who got their black belt from a school they were in, in person, etc. I do believe in good lineage as far as one getting their black belt from teacher in person and so on etc. However where I disagree is that a lot of "higher dan ranks" and when I use 95% I am speaking "higher dan grades as a whole" (most would be in the higher grades 5th - 10th) where received through correspondence and sometime through video exam. I would say Most 5th/6th and even 7th dans and above in Taekwondo got there higher dan grades from correspondence or from a martial artist possibly from another style. For an example...a very dear good friend of mine a current 6th dan in Taekwondo, excellent teacher, great competitor, huge school 100 plus students, very well respected all around New England got his 1ST through 3rd dan grades in person from a higher ranking Taekwondo teacher(who knows where his original teacher got his dan grades from?). My friend since he lived several states from his original teacher received his 4th dan in Taekwondo from the president of the Vermont Martial Arts association who was an 8th degree black belt in Shoryn Rue Karate.
My friend in turn got that 5th dan crossed ranked by correspondence to one of the Taekwondo Associations I believe you mentioned in your recommended associations!?
I myself got my 1ST - 3rd dans in person, my teacher moved and the founder of my system an internationally recognized Asian certified system "USA Karate Jitsu" died. So what was I suppose to do to move up in rank and give my students good credentials beyond my own start a new style? I loved my system..after 18 yrs I was not going anywhere else.