Ultimately, Apple will just doesn't want you to separate your data from the app. It's not just that it's a walled garden, it's a wall around you maintaining your data.
My primary tablet usage during the work day is taking notes. With a pen. And I've started organizing my notes into a self-indexed hierarchy of images. And for backup, those images go into S3. I can then just sync any other machine and peruse the images using Digikam which is kind of nice for a free open source app.
Every solution I've found in the iPad just requires you to put your data in some kind of isolated app playground, and then jump hoops to try to move it into any kind of backup system you can access on desktop OSes. I bought a Microsoft Surface, and despite not having worked in Windows in a decade or so, I was able to get my image-based note taking workflow done and set up in a day.
So, this iPad is a beautiful device I will never own. Purely because of their software policies. It's annoying.