I use a copy-on-write filesystem, so my on-disk usage would actually be much smaller (almost zero) if the backup files were copied uncompressed using a regular os copy (eg: Files.copy(src, dst, StandardCopyOption.COPY_ATTRIBUTES);)

I'll set this for !target 4.0 as part of the SPI rework. Should be pretty simple to add in an uncompressed full-world option.
Not sure what I'll do for naming each of these - I do want the names to be very self explanatory yet short.