A factory floor has 200 machines with no internet. You need to deploy a custom driver package. Instead of rebuilding the whole ISO, you create a DLC, inject it into the ISO using xorriso -update (without regenerating the entire image), and re-sign the UEFI bootloader. The factory boots the updated USB stick.
Ensure the "USB Device" is moved to the top of the boot priority list in your firmware settings. CSM/Legacy Mode: dlc boot uefi iso
function load_dlc_menu