> Google Takeout does solve this but but in weird hierarchies.

Surprisingly, the Takeout split archives can contain partial contents for a given folder or album. If you extract everything into a single merged root, you'll see both the sidecars and images in the same directory.

If you're on macOS or Linux, you can do this by mounting the tarballs with ratarmount and skip the extraction step. Details and links here: https://forum.photostructure.com/t/archive-file-format-compr...