Good day, thank you for Audacity.
I use it for editing long lectures (for example six hours of sound) and as a backup I need to save full project - maybe in the future I will need to change something or export to another format. I use 7z for creating single archive with aup file and _data directory - I found that 7z has the best compression for that kind of data. But compression needs some time (a dozen of minutes) and final size of the archive is a few gigabytes. But, for example, Adobe Premiere has a small project file (few megabytes), Sony Vegas too, Shotcut video editor etc. As I understand the directory _data contains an audio cache. Maybe is it possible to rebuild that cache when _data folder not found using project file and original source audio?
The last reason for smaller project filesize - simpler ability to use Git for that one xml-project file.
I think that this is a serious improvement that will make many users much happier.