For radios, the general idea of building radios to a spec and having them certified to be sold in country works pretty well most of the time. It might be nice to have a phone with plenty of flexibility on the radio, but I think most folks would be happy just to connect and send work-a-day packets OTA unencumbered by additional restrictions.

It seems like a hardware security device could act similarly to the radio in that the general OS can ask for service (e.g. a signature), but not have access to the internals of the MCU. I don't see why these systems need to be opaque either, in fact it'd be nice to know what is running on the security enclave or LTE radio, even if folks aren't generally meant to access/modify the internals.

It'll be interesting to see how things develop. In my case, I am looking for more experimentation with the smartphone form factor. I'd like to see better options in the market.