I've got a similar setup on GNU Guix, though I'm still refactoring the code (for this and a billion other features) and figuring out how my /home is going to work. I've gone ahead and copied the important parts out here[1] in case anyone is interested, but it's not great code, hasn't been tested, and isn't complete. Could be backed by BTRFS with a few tweaks (in which case the missing kernel bits wouldn't need worried about), and you could make root a TMPFS by just setting the `#:volatile-root?` flag of the `initramfs` procedure (in which case you wouldn't need rollback in the initramfs at all, just mounts for persistent data).

1: https://www.illucid.net/static/unpublished/erasing-darlings-...

edit: oh, lol, didn't escape the heredoc at all, import zfs / other guile modules, or put parted in the shebang; ah well

that's what i mean by informational