Seriously though ... most people are unabable to deal with a real kiai, even if it is for your own personal bolstering of getting the beginning effect of sound, movement, awareness for doing techniques. In the normal situations, kiai's are only used in practice where each of the participants are at equal level, or at least training at a safe level, and they totally trust each other not to go so far as to have serious injury, maybe just a bump or minor bruise, or two.
Funny you should bring this up? I have a condition where I can't get enough blood through my liver, which is one cause of dizzyness, and went two rounds of practice with jo where I was beginning to feel the dizzyness, so I used my most basic grunting kiai. My teacher knows how I push myself beyond what I should, so when he saw me pushing myself, he knew it was time to barge in so I could sit, not an uncommon occurance, but he had this big cheshire cat grin as he asked to barge in? I guess he was pleased to see a little bit of spirit in practice for a change. although I did need to sit and get rid of the dizzyness and shaking hands, while I was using the kiai to practice, I did feel like I was being held up with a renewed energy.
There are a number of ways to bolster your energy, and increase the performance of your application in Aikido techniques, although it might be a narrow minded soldier preparing for battle attitude, I must agree that there are many good ideas that must be practiced, taken into practice, and used as the need arises.
The fact that a particular type of Aikido is done this way, or that way is usually the evolution of actual usage verses theoretical practice of what could be.
After dwelling upon the physical means of application, I am exploring the next level of connecting the thought to bolstering the bodies effort ... and there are some very neat tricks that give or take away power. A good kiai is but one of them.