Thank you for that response. Wise, indeed!
The thing is, these questions can be dealt with intellectually, but it has to be done far in advance of the situation--years in advance. If you think rationally about the reality of life and death, then preparation is the natural response. But "preparation" doesn't mean just going down to the strip mall and signing up for whatever is available. What's the saying? "Better one year with a great teacher than twenty years with a bad one?" It's amazing to me how many people, with a choice between a really powerful teacher or one who teaches pleasant BS, will choose the BS, time after time, art after art. If you want real quality, you have to seek it out.
Second, if you seriously pursue this, you will definitely run into people you cannot affect in any way. Think Minoru Akuzawa and Dan Harden. And I will throw in one you may not have heard of: google Edgar Kruyning.
These people have something that even years of the process I described above will not develop--or, it won't develop it consciously. The process I described will definitely take you far past the level of most mortal humans, but to perfect it requires conscious awareness and rational development, seeking the deeper reason why these people are immoveable when they want to be and unstoppable when they want to move. And this is not something they can really even tell you how to develop. Ordinary waza training will develop a lot of stability, strength and rootedness, but only deep training with an IS expert will develop what Ueshiba called Takemusu Aiki, in which techniques are generated spontaneously on contact. At that point, there's no need for intellectualizing because as Akuzawa Sensei says, "the body is the martial art."
However, look at William Gleason to see someone who took very good mainstream aikido and filled it out with deep knowledge of IS.
And look at O Sensei's students. Even O Sensei could not directly give this knowledge to anyone. They had to feel it in him and learn to produce it within themselves through thinking about it and practicing the methods he showed them in order to feel it within themselves. Without that knowledge, all "generic aikido" feels more or less the same. But with that element, it's a tiger made of fire.
The point is, no existing "art" or curriculum of study will give you much of anything but a return on your own effort. And if you're making effort like that, almost no teacher will be able to show you anything--not because of your "full cup" or ego or being "set in your ways." They won't be able to teach you because their bodies cannot affect your body. And then, poor soul, you'll be forced to search for only the very best to train with.
It's all a question of how badly you want the truth.