I was the one receiving such documents, in print shops and services bureaus for 30+ years! And yes, you can likely feel and hear that background resonating in how I approach organization in DEVONthink! 
Adding TextBundle to the list of supported formats (Mac & iOS) would make life so much easier and therefore would be much appreciated.
Support for importing and reading .textbundle is already included.
We do have something in the pipeline that may be a bit of a bridge between full textbundle and my method. Stay tuned for a future release and hopefully it will mitigate your anxieties. 
Thank-you for all the amazing work you put into DevonThink! I’ve relied on it for 16+ years. It unifies my iOS and Mac usage in a way that no other app or service even approaches achieving.
Thank you for those kind words. It does us good to hear that we’re having a positive impact on peoples’ lives, learning, business, etc.
And thank-you @BLUEFROG for elaborating on your MarkDown workflow! You rock the most!
Wow! You’re welcome and thanks for the encouragement! 