Add extra VPN interface in custom build

Is it possible to have an extra interface added like a L2TP VPN connection?

I would like to have my build autoconnect to a default VPN account so i can configure it from the VPN server incase the device needs to goto factory defaults or something like firstboot.

So far i found the file below that looks like it creates the entire network. (Please correct me if i'm wrong)


Is it possible and if it is could someone point out an example on how to let it create the extra interface during setup?

Thanks in advance