Thank you for what you've written. It's like reading a good book. At the end of the chapter, you're left with wanting to read more.
I have just a thought about the portion above. In regards to your plausible reason #1, I find it very unlikely. My reason being that some of the students of Morihei Ueshiba also met and felt Sokaku Takeda. Rather than noting that Takeda's skills were completely different, they noted instead that his skills were far better. In other words, if you look at those student's views, they did not liken Takeda as someone completely different than Ueshiba, but instead as someone far better at the same skills. And looking at Takeda, we can see that he instilled these same skills to a few other students. In that regard, Ueshiba can not be seen as being unique.
Well, I suppose it depends on the nature of genius and I think we are dealing with two here. I know of a proverb, to the effect that you cannot have two queens in the same beehive. With aiki (bu) do, perhaps we should slightly modify this to: you cannot have more than one queen in one beehive (to allow for many more than two).
I have not really spent much space discussing Morihei Ueshiba's relationship with Sokaku Takeda. The reason is that these columns discuss aikido and I so wanted to start with M Ueshiba, not with S Takeda.
I have read Stan Pranin's interviews with the DRAJJ students of Takeda, but there is really no objective discussion in these interviews of Ueshiba's skills in relation to Takeda's. In any case there is a Master-Deshi relationship here and it is very unlikely that Takeda's DRAJJ students would rate Ueshiba's skills higher than those of their own Master.
The same relationship can be seen in Aikido Modern Masters
and this is what leads me to have some distrust in the interview as a means of obtaining objective information. I know that Stan's interviews are all we have about the early history of aikido, but this in itself does make them objectve (with all due respect to Stan's obvious skill as an interviewer).