I have a prototype for multi-volume snapshots now that is working well in testing. It consists of a new systemd generator that runs in early boot and allows the content of /etc/fstab to be overridden on the kernel command line. This allows booting into a snapshot of the system state including auxiliary mounts such as /var, /home etc.

We are still reviewing the options for including this in the distribution and whether the functionality would be acceptable for systemd upstream but we hope to have more updates soon and will update the bugzilla as this work develops.