Do you really think Kisshomaru would have oriented the curriculum in a direction *not* approved by his father? While his father was alive?
Yes. In fact, one point illustrates this very well. Kisshomaru was setting up a public demonstration and went to his father about it. Kisshomaru expected his father to fly in a rage because it went against his father's views on aikido. What happened? Ueshiba gave in because he had already handed Tokyo over to his son. There are too many stories, articles, interviews, etc all pointing to Kisshomaru (and Tohei) making changes.
And before people get their dander up, yet again, I'll NOTE that I am not stating good, bad, right, or wrong.
The degree to which M. Ueshiba oversaw the details of the curriculum is debatable. The degree to which the curriculum designed by K. Ueshiba actually reflected his father's teaching is debatable. But the idea that K. Ueshiba just went off and did his own thing without worrying about what his father thought seems ... unlikely at best.
Or did these visits to Tokyo at which M. Ueshiba said "no one is doing my aikido" also lead to world-shaking arguments between father and son, the existence and content of which has somehow (I can't imagine how) failed to survive to the present day?
I think you're taking it too far. It wasn't that Kisshomaru created his own thing. He took his father's outline and made it his own. For example, Kisshomaru removed all those deity references to allow the message to be more acceptable to a world wide audience. He codified the techniques so that many people could practice and have something to focus on. Etc, etc, etc. Some of the message remained, some changed. Daito ryu aiki was gone, but the new version of peace, harmony, and love aiki took its place. (Again, read my note above.)
Ueshiba handed over Tokyo to his son and with that, he gave his son the leeway to do whatever he wanted. Kisshomaru removed Omoto kyo and Daito ryu aiki: The two major foundational influences on Morihei Ueshiba's aikido. Replaced was Kisshomaru's Modern Aikido. (Do I even need to say read my note?) Remember the one time Kisshomaru heard his father tell him he had done well? The question then becomes, was it that Ueshiba was proud that his son had kept Tokyo going and tried to follow in his footsteps or was it that Ueshiba was proud that his son had created something worthwhile and valuable on his own? I think it was the latter.
Ueshiba's ability to produce men of stature is never in question. His ability to teach is never in question. Ueshiba produced Tomiki, Shirata, Shioda, Mochizuki, etc in pre-war time frames and all in less time than he had with post-war students.
In both pre-war and post-war:
1. Ueshiba was hardly at the dojo teaching.
2. Ueshiba rambled on about spiritual ideology that few understood.
3. Ueshiba rarely explained.
4. Ueshiba just did whatever he wanted to work on.
So, ask yourself what changed from pre-war to post-war? It certainly wasn't Ueshiba's ability to teach. He had already proven that he could produce aiki men. It certainly wasn't his teaching methodology because pretty much all the students, pre and post war, say similar things about how he taught. Who was in charge pre-war and who set the training paradigm? Who was in charge in post-war and who set the training paradigm? What exactly happened to the sumo practice portion of training in post-war? What other practices in pre-war were dropped in post-war Tokyo? Why did some sought-after teachers in post-war train completely differently in their very private dojos compared to Tokyo hombu?
The spin created to attach Modern Aikido to Morihei Ueshiba was so ingrained and prevalent that many things have been overlooked. Even now, people hold onto certain aspects with a death grip and are not willing to look for the truth.
And the really sad part of it all is that the truth doesn't detract one bit from the importance of either Morihei Ueshiba's aikido or Kisshomaru's Modern Aikido.