Export, Merge and Reimport multiple libraries

[ZarK]

Okay, I have finally sifted through 10 terabytes of photos and videos using any tool imaginary, and am left with three photo libraries.

For the final step of cleanup I will need file-based access to them, so my plan is to:

• Export the three Apple Photos libraries to disk using osxphotos
  -- As is, including any edits, duplicates etc.
  -- With as much metadata as is useful for reimporting (ideally keeping any analysis metadata from Apple, face tags, album info etc.)
  -- Including live photos, spatial photo / videos
• I will do some scripted operations on the files including changing some names
• Lastly, merge and re-import (in any order) all photos to a new, primary library

I know I can reimport with --exportdb, but I guess that won't work if I rename files in the mean time. Would a sidecar file include all data that apple photos can make use of when reimporting?

Are there any useful way for merging, or would I have three separate imports to the same library?