UEFI: How to go about updating the ESP with loader.efi during installworld

I'm currently working on creating and updating the ESP (EFI System Partition) 
for UEFI booting during installation and installworld. 

During installation, with my changes it gets mounted on /boot/efi and loader.efi 
copied into /boot/efi/EFI/FreeBSD and /boot/efi/EFI/BOOT. An entry gets added to 
/etc/fstab as noauto.

The issue comes during installworld, where we'll need to update the loader, 
and I'm not sure how we should handle that. 
If NO_ROOT isn't defined, do we just "mount /boot/efi", overwrite the files then 
unmount it? What should we do if NO_ROOT _is_ defined?

-- 
Rebecca