My point is not that it's difficult to design a peripheral device that loads its firmware over SPI (or whatever bus). My point is that firmware for all supported devices must be maintained on the proposed external device.

What happens when you add a new peripheral device to your laptop that didn't exist when your read-only SPI-connected firmware repository was created? How do you solve this with less risk than what we have now? Eliminate hardware upgrades and peripheral devices in favor of disposable computers and e-waste?

FPGA: I'm afraid the FPGA argument still doesn't make sense. Sure, the community could create a "trusted" processor or SoC, but why use an FPGA over a custom designed processor?

If the FPGA is reprogrammed at every reboot, we now have to ensure this process can't be exploited. If it's never reprogrammed, why use an FPGA in place of a CPU in the first place?

I appreciate the input and perspectives, but I still don't see how the "laptop" described in the paper is advantageous. There are many promising paths that move us much closer to secure computing, but simply moving firmware around doesn't seem to move us forward.