[userbinator]

You connect that pin to a small switch in a not-so-easily-accessible place and tell the user to connect it whenever firmware updating is required. Something as simple as pushing a paperclip into a hole would be sufficient.

Firmware updates should not be "transparent", "seamless", "one click", or whatever other terms are used today to describe silent or little-noticed changes. They are modifying a very important part of the system, and the user has to be aware of that.

[spacehome]

For better or worse, that's definitely not the "Apple Way".

[userbinator]

Apple did do that before though: http://support.apple.com/kb/DL1283

[cnvogel]

Being in control of so much of your hardware of course some hardwired logic could be included e.g. in the keyboard matrix that would make some physical interaction necessary during firmware upgrades, but not require a hidden button.

Nevertheless, as long as such a button or switch is easily accessible, and not able to be covered by a seal, the system stays vulnerable to evil maids. And such a thing definitely wouldn't be the Apple Way™