So basically, your phone is still your enemy, and anyone with physical access to the device will eventually be able to defeat all of your safeguards. This same situation exists with laptops and other computers. Even if your entire system is encrypted, at some point you must enter a key. It would seem that anyone with physical access to the hardware can intercept that key by some means. The only "hard" problem is this ex-post facto style access where the keyholder is dead. I guess the cops will have to stop shooting first and develop better non-lethal methods.
My question is, since we now must assume that everything the FBI is proposing has probably been done, is anything safe? If you start from an initial state of not even trusting your hardware, how can you establish trust?