The licensing should (in theory) have FRAND terms and so might not be impossible. Couldn't someone just create their own chips? In the worst case, could someone be able to come up with a new protocol and start a new network (assuming they had the money?)

You can create your own chips but you will have issues obtaining a license to use spectrum in some countries. Often, licenses for spectrum where the device is licensed instead of the end user, require the device itself to comply with spectrum use requirements....since the user isn't licensed.