There are file systems, like zfs, that support transparent block level compression. This means that you can just copy a normal disk image file to the zfs partition and zfs will handle everything for you. The image can be mounted in r/w mode the way you normally would, because as far as you're concerned the image file is a normal (uncompressed) image file. Why not use that? Sounds way easier and safer.

But oh well, the author works at Red Hat so I'm sure they have their reasons :p