To be fair, all KEYDB would really need would be a fresh discatt.dat file, because the previous dump contained everything else. You can create a discatt.dat file by starting an encrypted disk back-up into a temporary directory, copy the discatt.dat to a safe place as soon as it appears (and it should be one of the first files created), and then abort the back-up.
For disks 2, 3 and 4, KEYDB would need a ZIP file containing each disk's AACS/ directory (no need for AACS/DUPLICATE/
) and is own discatt.dat file.