With the root of trust and original software wiped, what used to be, say, an iPhone stops being an iPhone. It becomes a generic computer with the same hardware. All the software designed to run on iPhones like the App Store is likely to stop working. You won't fool the user for long.

And this attack is already doable by simply replacing the iPhone with a fake. It won't fool the user for long either, but you get to steal a real iPhone in exchange for a cheap fake.