A Chrome extension (web store compatible) that will pull up a crosh window in the background and execute the "set_apn" command upon login to the device. This extension will be forced via admin console to certain users, any time those users log in this command will write the cellular APN on the Chromebook to a pre-defined value.
Do you mind to let me review your source files and I will try to fix the problem with it?
I have done chrome extension projects before and I am a good troubleshooter.
By the way, Because I am currently in military service, I need to go back camp tomorrow. We might talk about this project next weekend. I usually take vacation on each weekend and do work for you.
Irvin