When you say in-house, I'm guessing you're referring to some kind of ownership issue which validates a traditional approach.
No, I mean in-house. For the ryu. By the ryu.
Miyamoto Musashi strikes me as more of an individual than a follower but perhaps I am incorrect in my understanding of the man.
Most people are incorrect in their understanding of Musashi, yeah.
He was a teacher. He was an artist in a number of manners as well, but, in this context, the important thing is he was a teacher. And the document is a teaching document (a form of transmission specific to the school he founded).
Do you know why it was released in 1909?
That's the earliest publicly available publication in Japan... why then? No idea. It did help a resurgence of interest in Musashi, though, which led, in ways, to the Eiji Yoshikawa novel "Musashi", which also helped popularise him again, but is responsible for a lot of misunderstanding surrounding the person that Musashi was.
While several passages of the book are in allegorical terms based on specific sword/tactical concepts and teachings of his particular school (and thus largely undecipherable to us as we have no frame of reference), much of it illustrates broader ideas and principles (including some from Sun Tsu) that are understandable and useful to us in both small and large-scale applications. A carpenter being able to find a use for all kinds of wood being an example.
"Several"?
Look, again, people can find a range of different valuable lessons and ideas in the book, but, again, without the context of Hyoho Niten Ichi Ryu, and an understanding of the mentality of the ryu itself, such things are just not accessible in what Musashi was getting at. To take your example of a carpenter "finding use for all kinds of wood", that's from the introduction in the Chi no Maki, and the point there is in comparing the roles of the general to that of the head carpenter, in assessing all manner of factors. This is, more than anything else, job advice for Terao Kyumanosuke for whom the Gorin no Sho was written. The specific things to be considered are culturally dependent on the contexts he's discussing... while this can transfer across, it's also a part of the mind-set and tactical through process (strategy - hyoho) of the school, and something that is aimed at informing a wider view than just what's in front of you in the moment.
As one leaves the Fire book and goes into the Void, Musashi's longsword cuts in broader strokes, Five Rings going beyond the sword-specific tactical and into a more general view of life.
In the Ku no Maki, he is discussing a manner in which to ensure that you are still correctly following the way of the warrior as he lays out in Hyoho Niten Ichi Ryu and the rest of the book. It is not general, in fact, it speaks against generality in terms of views on life, realistically. So... that's a no on that one.
I believe his intentions for this book went beyond combat.
His intentions with the book were for it to act as a document of transmission to one of his top students (and successor) to Hyoho Niten Ichi Ryu, Terao Kyumanosuke. It was dedicated to him at the end of each section, and was given with the instruction that it be burned once read and understood. It is ENTIRELY concerned and dealing with his school of swordsmanship and hyoho.
Although familiarity with TMA combat enhances ones understanding of these non-combat lessons.
None of it is non-combat lessons, in the schools' view. "Let your everyday walk be the same as your combat walk. Your everyday mind the same as your mind in combat." "Practice martial arts (Hyoho Niten Ichi Ryu specifically) in a way that it is useful in all things, and at all times". Everything is done with a combat-ready mind and body, with an awareness and psyche thinking and moving in hyoho at all times.
That's the point. Without Hyoho Niten Ichi Ryu, you're guessing. And, typically, guessing wrong.
I have seen some books that attempt to use Musashi, Sun Tsu and even Atilla the Hun as templates for success in everyday modern life, and these have been largely deserving of your criticism that I've quoted. The main reason IMO is that the authors had no real MA experience and understanding (and thus no base of reference) so many of their interpretations were invalid or given inappropriate spin, the works just being commercial pandering to the general public and as you say, lack "genuine awareness and insight" and not accurately representing Musashi's work. So, we agree on this main point.
The official stance of the school is that we are happy people find their own value, but are a bit bemused by people thinking they know what is meant. The only ones out there with any real insight into the school are the edition put out by Kim Taylor, which is not a mass-published copy, and the one by David K Groff, who has studied a different line of HNIR to the Seito (mainline). All others are lacking... and even those are not considered official.
My conclusion is that by sticking to the stuff an educated reader can understand and discern, Musashi's book has applications and lessons we can use in a variety of ways and still stay true to his intent - I think to a greater extent than your post suggests.
No.
Let's be very clear here... Kenji Tokitsu is an experienced kendoka. Alex Bennett is a kendoka, Iaidoka, jukendoka, and practitioner of Tendo Ryu naginata (Koryu). Their translations are very good... but also flawed and inaccurate in a number of ways... words and phrases added that aren't in the original Japanese that alter the meaning, sometimes inverting it, based on their perspective and frame of reference... which, not being Hyoho Niten Ichi Ryu, is limited, despite the similarities and supposed links.
In any event, Go Rin no Sho is a fascinating work worthy of respect.
True.