[fn-mote]

I feel like I'm missing something here.

Honestly, if you can't update the firmware you're in the same situation... knowing that you have a critical vulnerability and unable to fix it.

Enforcing trusted operations is definitely more work than they are going to do (if it's even possible to "do this right").

In a semi-ideal world, I would look for a vendor that permits only certain ops from a flashed image and hope that their crappy "restriction enforcing" code is also riddled with vulnerabilites so it's really just "follow the rules please".