there's not as much attention on this as there was when they tried to implement it in their browser, so sadly I think this will eventually come to be :/
yep. and i wouldnt be surprised if that was intentional. how quickly they backed off on that one very much smells like a classic door in the face tactic. this whole WEI thing is far from being over
The solution is the same, though. Chances are non-Google Android forks aren't going to implement this, just like how Chromium-based browsers that aren't Chrome (or Edge) ended up implementing solutions for the depreciation of webRequest in Chromium's implementation of MV3. So if Google does do this, just unlock your device's bootloader and flash Omnirom or another Android fork onto it.
Won't work sadly, if you install a custom OS your device will not be able to attest to it being original, and play integrity won't pass (which would by extension include WEI). Not providing the results will be seen as just as bad as not passing. So as long as the vast majority of mobile users have it deployed you're screwed.
You can think of it as requiring everyone to wear a cryptographic ID badge to do something as simple as going to the store to buy groceries. You can always not wear it, but you will be denied service just as someone who has a "made up" ID.
The evil exists at the silicon level where they cryptographic keys are hidden from the user.