So let's you and I try to come to a consensus here and now as to the next effort to be undertaken in this regard.
I think you've pointed us in the best direction with that current HUD article. It is this: what's with all of the focus on visual information?
A human being is way more than floating eyes; in fact, the eyes are the most cognitively expensive feature. Overlosading it is easy to do, even by accident.
The thing is, a human pilot doesn't need to see most of the gauges. Most of them show numerical information with far greater resolution than is usually necessary. For example, altitude to the foot is not necessary outside of landing scenarios. Being able to see through the plane is completely useless when nothing is there.
But I see a human being sitting in a chair. Not walking, not running, not smelling, not tasting, not feeling a temperature, not being hugged, not being caressed by a loved one. There are so many human faculties -- most of which are wired directly into the human spine, and one wired directly into the human brain -- going almost completely unused. Why not tap into those?
A pilot could easily know where the bandit is by a simulated caress (or vibration) on the relevant part of the body -- upper back, lower back, left shoulder, right shoulder, et cetera. Visual HUD information can be the detail upon request. Here's a thought, how about a gentle pull of the neck towards the bandit. Easily felt, easily overcome.
I've got one of those non-fan heat dishes for my grandmother. It's basically an IR heat-ray. Altitude could certainly be conveyed by the localized temperature in the cockpit, or in the helmet. A ten degree range would be easily understood, and a twenty degree change even more so. Colder at high altitude makes sense.
There are myriad tactile sensory inputs to be used, including a gently squeezing of the upper arm as a fuel gauge. The really amazing thing about any such system is how the brain adjusts memory as a result - with different memory banks for high vs low altitude because of temperature sensation -- something a numerical altimiter can never provide.
In any event, to summarize, I see a few dozen inputs into the human brain, and I see only the visual cortex being used.