Ah, got it! Sorry for us talking past each other there, then. I think part of what I was suggesting still applies there: if you can't install things remotely,

Ah, got it! Sorry for us talking past each other there, then. I think part of what I was suggesting still applies there: if you can't install things remotely, and you have oversight to ensure that any backdoor applied to you has to have been sent to everyone (which provides a measure of security), then what's left is physical control of the device. For instance, keeping the device in your possession, locking it down against peripherals... That can't prevent you from being physically coerced, but it provides a lot of security in every other case. And if things have devolved to the point of you being physically coerced then you have much worse problems.