Comment # 12 on bug 1126900 from Ignaz Forster

I'd suggest to still solve it, I've been thinking about it for quite some time
now. To do so my plan is currently as follows:

* Create a subvolume "/boot/writable" on read-only file systems (we need that
anyway for Ignition to be able to store it's flag file) in
"read-only-root-fs"'s posttrans script. A fixed subvolume name (in contrast to
/boot/grub2/<arch> / /boot/efi as originally suggested) has the huge advantage
that it doesn't need guessing where the file could life.
* The package will also introduce a GRUB configuration snippet, trying to
additionally read the environment block from "/boot/writable/grubenv".
* health-checker would then be changed to write to that file instead of
"/boot/grub/grubenv".

This doesn't solve the problem that other applications will not be able to
write to the environment block / have to be explicitly made aware of the new
file location, but I guess we don't want to change the default location of
grubenv either, do we?