It's an ancient and commonly used concept, Graham. While it's a revelation to most westerners, the concept of blending/mixing/combining with an opponent's "ki", it's a concept that has been around thousands of years. Reading the classics and being around Asian martial arts, Ueshiba would well have been acquainted with the term/idea. What's interesting is that once you understand the concept and think "Voila!", you begin to look around and say, "wait a minute.... I wonder if the old translation of 'using the opponent's strength' may have been more to the point of what they were saying?". In other words, there were lots of giveaways like "kuzushi" and "using the opponent's strength", but we all took them to mean the physical stuff that we could relate to in our own ignorance.
That's what I question. The term, not the idea. I've seen it mentioned to do with 'some' arts way back and never exactly the same.
The mixing, blending, combining? These words may well have been used in certain arts in the past and even today but they are not the terms mostly used by O'Sensei and thus his meaning for AI KI or even Ki.
He most usually used the words harmonizing, harmonizes.
The logic that O'Sensei knew about these historical and oriental views means that's what he meant is what I always disagree with for to me it's patently obvious he didn't.
That's why I like to find out what your view of Aiki is as different from O'Senseis not to make yours wrong but to see the difference.
It's simple really. Aiki prior to his AIKIDO had a meaning obviously and was no doubt to do with to whatever degree what you say. That's all good and useful to know and do and thus help make sense of some of Aikido.
However, his explanations of Aiki and bu and Budo and Ki were different and it's that difference which made Aikido. Such is my view.
I'm also learning from this that there are descriptions of heart, thus desire leads mind leads ki etc. Once again I then understand where others get these Ideas from and no doubt these are old chinese concepts from various arts.
However I have never heard or read of O'Sensei or Koichi Tohei giving that sequence or holding that belief. In fact Tohei said the sequence is simply spirit-mind-body or ki-mind-body.
This indeed may have led to those old heated debates between chinese and japanese as to Ki being different to chi.
This will at least give you how some in Aikido relate to Aiki and thus see other views of it as different and belonging to something else, whether it helps Aikido or not.
It's all interesting nonetheless.