Thank you for the link. I'll be looking into it. Expect a reply soon.
A Few Thoughts, after a briefly skimming through the sites.
I wonder if I could use EFI and include it into a new Live CD written on my own. That, I think, is the key here. I'd do my part for myself, and it might take a bit of coding.
It would boot off of the Live CD, and as things are come across as unsuccessful, it just proceeds until it succeeds or doesn't succeed for a boot.
Boot Camp: It comes up with the choice: Boot up in Windows, or as the macOS. I wonder if you boot into Windows and then run the Live CD off of that. It's different, than the OP, but it seems you'd have to quickly press [the key(s)] for booting. Its been some time since using Boot Camp, so maybe I'm wrong there.
This is all about data recovery, and using a Mepis Live CD, would get it all off.