OSTree wants the initramfs images to be immutable and generated on a build server.
systemd wants /etc/machine-id to go in the initramfs.

The intersection of these - gnome-continuous and rpm-ostree hardcode machine-id.  This is suboptimal.

Possible fixes:

 - Teach systemd-in-dracut to synthesize a machine-id in the initramfs, and copy it to /etc when the system boot
 
 - Add a new "machineid=xxxx" kernel argument.  OSTree would generate one if it didn't exist.  Systemd would learn to read it (probably write it on boot to /run, so other things picked it up)

 - Concatenate initramfs images: I think I saw some people discussing this elsewhere.  Then we could make an *additional* initramfs that contains /etc/machine-id per client, and have that be an overlay on top of the stock dracut (or whatever) generated initramfs.