ONT DHCP WAN Interface with Automatic User ID

Hi guys.

I'm using DHCP addressing on my ONTs wan interface. I can manually set the user ID field like the image below:

Is it possible to auto-fill this value with OMCI serial number? Inspecting the config XML file, I can see its value:

 X_HW_ClientID=""

Is it possible to generate its config file using some variable or macro, to force ONT to fill this value with the ONT serial number by default? something like:

 X_HW_ClientID="%ONT-SN%"

This would be very useful to map and keep track of customers' IPs on the DHCP server. 

Regards, Leandro.