Try changing the default DNS in AOSP from 8.8.8.8 without doing ill advised, hacky weird nonsense. Have you tried to prevent your AOSP phone from reporting tethering to your carrier in the last ~6 years? The software is licensed GPL, which means you own it outright as a user, to it's core, right? So these types of things should be possible with ease with a little technical proficiency, right?
Android, including AOSP, is not an operating system, because it doesn't enable the user to operate the device. It is a kiosk, because it enables the licensee to use the device, and limits utility to OEM, carrier and Google market requirements and business cases.