A new work-in-progress feature for systemd is "PathImages" though there is a suggestion this option be renamed to "MountPaths", but in any case is about allowing arbitrary images / block devices to be mounted at any path by systemd.

Systemd already has the RootImage= option for taking a block device node or file-system image to be mounted for the root directory. With the proposed PathImages feature, it would allow mounting arbitrary images at any path and supports specifying different mount options from the systemd service files.

This would make it easier on various customized systemd use-cases and other situations where for a systemd service you may want to mount a file-system image automatically for a pre-defined path.

This systemd PathImages feature is still being worked on but the current material for it can be found via this pull request.

Some other systemd features being worked on early this year include a new PermanentMACAddress= option, logging / information improvements, fixes, and it also looks like systemd-homed might be merging soon.