I used a similar trick to stuff 14 Linux distros onto a 6 GiB sized SD card image using btrfs filesystem. The distros share a lot of common files, so this works

I used a similar trick to stuff 14 Linux distros onto a 6 GiB sized SD card image using btrfs filesystem. The distros share a lot of common files, so this works well to save space. (btrfs also supports the data block sharing CoW feature as APFS) https://xnux.eu/p-boot-demo/ https://xnux.eu/p-boot-demo/ I had to write a custom tool to do it efficiently during image creation.