Installing ESP on software raid may not be a good idea, even if raid metadata
is at the end of partitions.
Perhaps, a better approach would be to add procedural ESP duplication via hooks
in grub and whatever else needs to write to /boot/efi (potentially
debian-installer?).
Basic concept of a mechanism: use ${PRIMARY_ESP_MOUNTPOINT}.${NUMBER} as
location for ESP duplicates, like /boot/efi.1, /boot/efi.2, etc...
After writing to /boot/efi, also check fs, fstab for expecded duplicate paths,
sync contents to all found duplicates, then add duplicated entries via
efibootmgr for each device.
