I got so focused on the "internal power" aspect of internal power that, as a friend of mine just pointed out in a personal note, that "it takes two to tango." It's not just about cultivating energy - it is skill and energy that is not only exerted upon, but created through working with/on another person. To be clear, one cultivates within oneself abilities that make one able to work with/work another. As my friend wrote: "Whatever you are doing internally/IP-wise with your body, it will take uke along for the ride."
My friend writes, "The components of training aiki are part of IP method --the "powerful effects within the body" (your body) you wrote of -- not aiki itself. There must be IP to make aiki, but IP itself is not aiki."
What this means is that IP is not just another way of "power-up" weight lifting through another means. To be sure, some people use these methods and become very physically powerful. Wang Shu Chin was witnessed by a friend of mine literally shaking (!!!!!) the huge torii at Meiji shrine.
But that will not necessarily make THAT "internally powerful" person more powerful in interaction with another.
(I remember that Sugino Yoshio attempted to refuse to compare Takeda and Ueshiba, but signficantly, he said something like it was not necessary to say that Takeda was a ten and Ueshiba was an eight: both were great). In other words, the physically older and weaker guy was still more developed - and perhaps, able to do more in this area.
A final story to illustrate my friend's point. Cheng Man Ching, perhaps not nearly as good as Robert Smith described, but still pretty exceptional: he decided to learn bowling in New York and quit because the ball was too heavy for him. Too heavy! This guy that was seen sending people flying off their feet to crash into walls.
I guess it all depends on what you mean by "power" in IP. I study a derivative of a Chinese martial philosophy that you could legitimately say is almost mono-focused on explosive power. Yet, even within this framework, is the idea that power is
change, or rather, it is change that makes power, and the ability to deploy constant and rapid change, as well as cultivating the level of reactiveness to make those rapid changes a response to the outside world, not just an internal monologue or pattern, is fundamental to the expression of it. No change, no power - no power, no change. That's not even really a quaint aphorism, once you dissect it, you realize all actions of the body are synthetic/artificial, and that the body is constantly responding and balancing forces at any given moment to accomplish what our mind sets it out to do. The exact relationship of this to aiki I can only speculate, but even still, just the subject of "power" is a lot deeper than it seems.