Hugh - One thing you didn't include:
That Ueshiba included all of these definitions and more, not as an amalgam, but in the same way that light is both a particle and a wave, depending on the viewpoint of the observer. I truly do not think that Ueshiba had a public definition of aiki and a "real" one - they were all his definitions, and to him, all true. That is why, I think, people who wish to do so-called "O-sensei's aikido," while also studying IP/IS have more difficulty than someone studying a martial art that takes a technological approach. A lot of these arguments really come down to an insistence that one's preferred definition of aiki is correct. That there would be a single rather specific definition is almost surely true in most other martial arts that do internal training (although I once had a t'ai chi guy in Taiwan go into a screaming rage at me when he heard I did xingyi, because, he screamed, xingyi was too aggressive).
But what those in these arguments seem to have difficulty with is that Ueshiba himself gave equal valence to all possible definitions. Again - because I'm sure this will be misinterpreted by someone - that light is both wave and particle in nature does not mean that it is" half wave" and "half particle." Nor is it "both." It is, simultaneously, 100% each. Similarly, that "aiki is love" or "aiki is blending with the energy of one's attacker" or as Andrew Prochnow so elegantly put it, "Aiki is the result of one training their own body to be in unision with itself. Structure gives the Aiki a clear pathway to follow. Relaxation enables Aiki to travel through that structure. Intent is what fuels the Aiki in the body. When one comes into contact with one who has trained their body. Aiki is what is seen when the two meet," or even more definitions that surely the assiduous could find when researching Ueshiba's quotes and films, are all Ueshiba's aiki. In my opinion, if one wants to do aikido, one has to have the courage of not having such strong convictions - except that studying Ueshiba requires an acceptance of paradox.
This is a very nice post.
Also, just simply the idea, and I think Mr. Amdur presents that above (please correct me if I'm wrong), Ueshiba and Takeda were both using the word to represent what they were doing. That could be lot's of different things. They both claimed it, and used it to represent them. After them, their students did the same. So we have lot's of different, legitimate definitions of the word.