> The main exception to this, I believe, would be for critical systems where compromising operation through software modification presents too high a risk. Examples I'm thinking of include:

    > certain medical devices, such as implants and insulin pumps
    > subsets of electronic control units for cars

These are precisely the opposite of what should be exceptions. If you have a pacemaker implanted in your body, you need the right to replace whatever software is running on it before the manufacturer goes out of business and takes the signing keys with them.

There exists no thing where the owner of the device should not have the right to replace the software it runs, and the more safety-critical the device the more important the right.