Hi! The solution for this is already available in the patch series in <http://issues.guix.gnu.org/48314>. The new grub-efi-netboot-removable-bootloader can be used for this.
Technically there is no big difference between an installation to boot from network or from local storage. For booting from network two symlinks are needed, which can’t be created on an EFI System Partition with its FAT file system. In the later case a small intermediate grub.cfg is created, which allows booting from local storage. Bye Stefan
