or if it's confiscated and you're compelled to unlock it.

It seems like it'd be a lot easier to compel someone to unlock a phone using FaceID than TouchID and that scares me.

The names FaceID and TouchID are apt. They are IDs. Not passwords. You should unlock your phone by something in your memory. Unlock by face or fingerprint is an anti-feature for me.

Perhaps, but what if they ensured that FaceID only worked when you had both eyes open? It would then, be much easier to be non-compliant than it would with TouchID since it's harder to hold someone's eyes open without obscuring the face than it is to press the phone's home button against someone's finger.

Wink/Blink if you don't want to unlock your phone seems, to me, to give more consent to unlock than a fingerprint.

Ah, yeah, that's what I was trying to get across

When you record your face for the unlock, strike a pose that is not your default expression. Put your hand on your face with the sherlockian "hmmm" expression.

Guards/police won't know, they'll just hold the phone up to your face and try to unlock it.

Since it seems so much less invasive, I'd be worried the the arguments that you shouldn't need a warrant to do it will seem much more persuasive.

iOS 11 will force a PIN if you press the Home button five times (or, on the iPhone X, probably if you press the Siri button five times).

If they remember to look away, it won't unlock. Seems very unlikely to me.