I think I am getting a better picture of what you are saying. And it seems to me like your model may make sense from an analytic perspective (thought I'd like to see a way to do some data analysis/motion capture etc)
So here's how I train (keep in mind I am pretty much a beginner at this aspect).
The best way to demonstrate what I mean by "pressure" is by showing a process by which you can also develop this feeling, since it's not something I can measure or show with scientific instruments _at this time_. That's a key comment. I AM NOT saying this is not measurable by science, or is not a regular explainable phenomenon. I just don't know what it is. I am open to investigating this with FMRI, motion capture, EEG or radioactive tracers in the blood , but I lack the facilities or the expertise to do that.
Onwards...so if you take a look at the yoga position "downward facing dog"
Once you get into the full posture, if you experiment with your breathing while staying as relaxed as possible eventually you'll feel that the the expanding and contraction of your body created by your breathing, changes the amount of pressure you feel in the palms of your hands (from the ground) as well as the feeling of pressure _inside the arms and shoulders. It will also change the feelings of pressure in your legs and at the foot-ground interface, assuming you are flexible enough to have your heels touch the ground. (took me a year or so). You will have to build up the muscular endurance to reach this point, which can take a few weeks. that is, you have to be strong enough to hang out in the posture long enough to feel what's happening in your body. Hardcore yoga peeps call this "prana" and that's fine they can call it wtf they want but to me it's just a feeling, and not some metaphysical thing that involves channelling the power of the universe.
Okay so on to the breathing:
Basically there are two schools of thought on breathing. Some yoga ppl say that you should always breathe "abdominally." This does not mean you actually put air in your stomach. Obviously not. What it does mean is that when you inhale, you let your stomach muscles expand, and when you exhale it flattens toward your back. Your chest does not rise and fall much when you do this.
The second school of thought is that you should always keep a flat stomach. This is a pilates thing that you may be familiar with. For the non-pilates ppl, the flat stomach is the feeling you get if you put your fingers on spot where your inner thights meet your pelvis. When you do that and cough, those are the muscles you keep flat. If you do this, you flatten the stomach muscles toward the spine, and therefore when you breathe your chest will expand and contract.
If you get into the downward dog posture, then alternate the types of breathing you do in cycles (flat stomach/stomach expansion) you will begin to eventually feel the sensations I have outlined above.
Once you do that you will feel how what you are doing is feeling how the weight (mass times gravity) of your body is distributed, and how your breathing changes that.
The weight of the body is simply a force (f=ma) and of course you can create (some) force on/in your body (i'm not sure about the exact terminology here, nor how it works exactly) through muscular tension. The next step, once you can find the feeelings of pressure in downward dog is to recreate those feelings while standing up. You can do this by playing around with the tension created when you extend or contract your arms, flex your wrists, open your hands and do things like...make those weird hand positions (crane beak, sword hand, leopard paw, etc etc) you see in Southern Shaolin and karate (esp Okinawan karate)
Now take those feelings you can create in your arms and upper back, and recreate it while standing up. At my stage, I use some overt muscular tension to create the pressure, then try to let it go. When I set to do pushout, I create those feelings right before my training partner makes contact with my hands, and I strive to maintain them throughout. Once I accept the force of the other person, I try to feel it in my feet. I've noticed that the harder they push the more I feel like I am being driven into the ground. My theory is that somehow I'm translating the push in Z into a Y force that increases the normal on the shoe, and thus the force of friction which keeps me from being knocked back. Now that I think about it, I should get some scales and test this out.
As far as kokyu ho stuff, I never did it when I practiced hapkido. Once in a while one of my friends would teach what I now realize is a tension-based qigong exercise, but none of us (including him) realized how to use it to develop what we are discussing here.
This is kind of odd considering that a number of my former club mates were ranked (dan ranked in some cases) in aikido, but so it goes.