The first article says they are just storing a secret key on the SIM and on the network provider's systems. That is just dumb and was totally insecure even before this happened. They should be using privat/public key pairs in which the private key is generated on and never leaves the SIM.
Symmetric cryptography is not "totally insecure", and there's no reason to accept the complexity, large key size and performance hit of asymmetric cryptography when there's a perfectly reasonable key distribution mechanism in place. Further, your proposal wouldn't even help... who cares if the private key was never off the chip? Given a public key how do you know that the corresponding private key was ever on any chip? Answer: You need to obtain the public key in a secure fashion in a controlled environment, such as during manufacturing. If you drill down on the requirements for the context and process needed to identify that public key as trustworthy you find that you have exactly the same requirements for a secure symmetric key injection, which is much simpler and easier to manage.
And as for attack by NSA/GCHQ, if those are your opponents, and they're actually focused on you, you can't win. At most you can make them work for it a bit, but not very much. So it really doesn't make much sense to include national intelligence agencies in your threat model.
