Re: Ueshiba taking Ukemi
Mike - It may well be as simple as that in part. The seminar format does not lend itself, as you say, to taking ukemi for the students. Add to that all the descriptions of Takeda being at a level of true paranoia in regards to being vulnerable to anyone. (For example, berating his son for walking in front of a personal friend who was a sword expert, because the guy could suddenly take it in his head to strangle Tokimune, or when he went to visit Ueshiba, pulling the table next to the wall, and sitting so no one could get behind him, etc.). Whatever the merits of all of this, it's hard to imagine Takeda deliberately creating an opening.
I think that, as a corallary, as he taught this way, his students did too. Let's imagine his method was showing the technique and giving instruction not only on the technique, but also on whatever exercises were necessary to develop the ki/kokyu. Some people - like Ueshiba - get really strong. But the potential pitfall would be a) grandiosity b) that the students are taught to tank, under the illusion that falling that way "has to happen."