Re: Is two Days a week enough?
Let me start by saying that I am *not* dismissing Saotome sensei or his skills. Or for that matter, even his personality -- I am told he is a great person.
But, the notion that most post-war students had extensive hands-on time with the founder ... it's very hard to support. Don't take that as meaning post-war deshi weren't skilled. As you noted, some were, some weren't.
As for pre-war vs post-war ... egads, it's nearly identical in regards to hands-on training. You should see the small amount of notes I have on it. There was no extensive hands-on training with Ueshiba Morihei then, either.
Which begs the question, what was different? How did Shioda, Tomiki, Shirata, etc get so good so quickly? You can't just say it was the Daito ryu training because we have thousands studying with Takeda and not getting good, you have the whole Modern Daito ryu world that is pretty much in the same boat as the Modern Aikido world (all technique and no internal skills), yet there were people who *did* get significantly better.
We can definitely say it wasn't the overall length of training. There are people who have trained 2-3 days a week for 40 years and aren't at the level of Shioda, Tomiki, Shirata, Mochizuki, etc.
We know that Shioda and Tomiki trained in 5-10 years and got very good. We know that many of the "Giants of Aikido" came from the pre-war period. I have notes that show that those pre-war students didn't have extensive hands-on time with Ueshiba either.
By deduction, we can rule out training for lengthy times per week over the course of decades, training for very short times per week over the course of decades, knowing hundreds of techniques, and not having extensive hands-on training.
What's left then is my theory: Ueshiba during the pre-war period was not yet fully developed in both his martial abilities (aiki) and the Oomoto kyo doctrine (spirituality). He was a work in progress in those years. When those pre-war students trained with Ueshiba, they were seeing, having it explained, and hearing the training in somewhat more simplified terms. These pre-war students were able to "steal" the working knowledge of how to start training aiki. Not the complete package, mind you, (read the Sagawa book and notice how he spent long years trying to become "sticky" because Takeda wouldn't teach him) but enough. It wasn't the techniques nor extensive hands-on time, but a very specific manner of training that had to be explicitly shown.
As the years passed and Ueshiba became more proficient in both, his explanations became more ... spiritual. Or as many said, they didn't know what he was talking about. That created a very large obstacle to learning aiki. Of course, you can also theorize that Takeda was angry that Ueshiba was showing people the "secrets" and Ueshiba just started using spiritual terms to hide his attempts to teach people aiki.
That brings us back full circle to "Is two Days a week enough"? I think you covered the answer very well for Modern Aikido. No need to repeat what you've already said throughout this thread. For Ueshiba's aikido, the answer is no. Neither in partner training, nor in solo training. Ueshiba and Sagawa were prime examples of just how much *correct* training was required.