I think i get your point. But IMO it's not plausible, especially about revealing government have access or backdoor to people's devices with ability to steal or take away people's asset.
Why do you think is it not plausible?
I barely understand what is subliminal free signatures. But,
1. Using software which choose nonce or K value carefully could avoid private key leak/recovery. RFC6979 handle such task.
2. Not re-using address means you avoid such concern.
I'm no expert but it means signing transactions in a why that the person signing knows that their keys are not being leaked via some secret channel.
I'm not sure how a user checks the implementation of RFC6979, that is, how can in independently verify the correct nonce was used? In any case, the keys could, in theory, be leaked by some other means e.g. via steganography.