It sounds really lame to say, but it feels like what you're suggesting is the exact opposite of what the market wants. People want a device they can give to their kid without worrying that they'll mess it up.
And I don't think this is an issue where any side actually cares about freedom; you allow proprietary software on Cydia, which sort of kills the user freedom argument, but even then, people would still be free to just buy a phone that supports them using their phone in a way they want to.