"Documentation" isn't all you crack it up to be... Isshin Ryu has been having document wars for years, mostly because Shimabuku Sensei had a sense of humor and told everybody he promoted and sent to the United States that "you're in charge of Isshin Ryu in the U.S.". Over the years, I've seen some absolutely hilarious confrontations over "documents" that were "issued by so and so"... "These are fakes because he only used RED ink when he stamped certificates..." and it goes on and on from there.
If you founded a legitimate style, the technical and "legal" aspects of it are pretty simple. You document your techniques or the methods being used, and then perform the techniques before a legitimate organization who can determine if your methods and techniques meet "muster". If they do, you can consider yourself "legitimate", if not... it needs work. It's the example set by the Danzan Ryu style of Jujutsu.
The paper trail of "styles" and systems are all pretty well paved with "fees" for testing and certificates, and you can find all kinds of "crossover" ranks issued for switching from one organization to another one... with or without a test, that are all "mainstream" martial arts. Now that "certificates" are money makers, the organizations do all they can to keep the cash flow increasing... up to and including sending certificates by email.
One of the reasons I always sought out "master instructors" was because their reputations and organizations were all solidly built on good martial arts. There were always "splinter groups" that came off them, but the main thrust of training with a true "master instructor" doesn't change much.
Two of my old teachers are dead now, and I don't have a certificate from either one of them... but I valued their teaching and friendships very highly. You're welcome to razz me about the "studied with dead instructors" if you want to... but it didn't happen in a vacuum... there were plenty of other people there to witness our training... and unless you're claiming that you trained privately with one of the dead masters, there should be corroberation that you did... pictures with them, if nothing else.
45 years ago, there were no "organizations" that were certifying anything to do with martial arts. We had to drive for hours just to find instructors... some good, some bad... and we ran into plenty of them that left Japan or Korea as a nidan and landed as 6th, 7th, or 8th Dans or "master so and so"... The legitimate ones "had the goods"... the others, just ran scams...
In the late sixties or early seventies, the U.S. Judo Association sued the International Judo Federation over the issuing of rank certificates and their use as a means of keeping American competitors out of international judo tournaments. The finding of the court was that "all rank had to be accepted in open competition", and that each country should set up a governing body of it's particular sport to oversee that function. Today, there are still splinter groups of every martial art, no central authority(except in a few sports that are done at the Olympic level) and all the hounds still baying at the moon about "legitimate" and "illegitimate" rank.
To show you how crazy it is, when I tested for my Nidan in Judo, I scored high enough to be ranked Godan (5th Degree). I had no longevity with the association where I was testing, so they would only issue the Nidan certificate... for years, I got a letter every year offering me some kind of promotion if I just sent in my money, and was actually offered higher rank than I scored on my test when a splinter organization started up... so much for "testing standards"...
The proof of martial arts is "on the floor" and "on the mats". Training is training, and it can be good or bad... want to spot a faker?... put the pressure on him in a class or in randori... not in a chat room. If he's any good, he can stand his ground.