Great writeup! As an AR UX designer I completely agree on the HCI chapter. Tony Stark might look cool while he’s waving around, but it’s not a comfortable way to interact. The current inputs seem to ignore the basics of last century’s ergonomic studies. It’s a tricky problem to solve though. Gestures lack feedback, speech lacks accuracy, and keyboards defeat the purpose.
Personally I have a lot of faith in combining gaze for aiming and a Manus-like glove for handbased tactile selection. Whilst holding your hand up and pointing it requires sight and a significant effort, most user’s spatial awareness let them tap their pinkie to thumb without watching. No more holding your arms up just to select something!