So, as I understand it, your ripper produces a structure like this:
├── audiobook_title
│   ├─ First_disc
│   │   ├── Track_1
│   │   ├── Track_2
│   │   └── Track_3
│   ├─ Second_disc
│   │   ├── Track_1
│   │   ├── Track_2
│   │   ├── Track_3
│   │   └── Track_4
│   ├─ ...

But you want them something like this:
├── audiobook_title
│   ├─ 001 First_disc_Track_1
│   ├─ 002 First_disc_Track_2  
│   ├─ 003 First_disc_Track_3
│   ├─ 004 Second_disc_Track_1
│   ├─ 005 Second_disc_Track_2  
│   ├─ 006 Second_disc_Track_3
│   ├─ 007 Second_disc_Track_4
│   ├─ ...

And there's nothing in the folder names (First_disc, Second_disc, ...) which is in a fixed position that you can sort on - unless you add it yourself (eg. 01 First_disc, 02 Second_disc, ...)

Is that right?

If nobody comes up with an easy way of doing that, It should be possible using a script - though I'm not very familiar with Windows scripting. It could copy them based on the date on which each file is written. (Assuming the ripper writes them one at a time - mine does several in parallel, but can we told not to.)