This is getting very interesting, indeed. Thanks, Peter, for taking the time to share your knowledge.
I can understand that Osensei used the concept
takemusu aiki intimately linked with his cosmology, his spiritual world view. That would indicate a proper interpretation of his use of the term, being sort of more symbolic than practical.
He would not mean something like "with aiki you create the most effective budo", or for that matter "improvise budo techniques that agree with the aiki principle".
It seems he has combined two concepts, each with a vast and complex meaning to him:
takemusu and
aiki.
Maybe we should investigate what he actually meant by
aiki, as well? That has surely been done. Anybody got the facit?
Can it be sort of a koan? Was Osensei using the term
takemusu aiki, well aware that most of his students would not understand at all? Peter's experiment with his students implies it.
Peter, is it possible that Osensei saw it so that budo has gone through an evolution (takemusu), where aiki is the optimal result? On that note - did he ever consider the possibility that budo could evolve higher than aikido?
Sorry for adding so many questions, and not contributing with any answer.
PS: I believe that a westerner easily forgets about the significance of the Chinese pictograms, making up the words in China and Japan. The kanji lead to a slightly different intellectual process, from that of our sound-alphabets. Their writing is built on images instead of spoken language. This has to be taken into account - just don't ask me exactly how
Probably, it makes sense to stress the importance of analyzing the specific kanji, their components and in what contexts they are generally used.