Chris - small question.
This cosmology is it separate and distinct from Omoto-kyo or intimately tied in. I know I am asking for a fine line to be drawn in a somewhat hazy landscape but it is a question that springs to mind.
There is more than one close student that felt a close study of that sect would help to understand Ueshiba's aikido. I know Tomiki made a point of it but I never got a clear indication whether he found it particularly useful.
That's a good question - the short answer is that I wouldn't bother unless you're specifically interested in it, but that a good working knowledge of Shinto in general is useful (essential?) to decipher what Ueshiba was talking about.
Omoto-kyo can be different in some ways from regular Shinto, and Ueshiba's personal interpretations can get a little different from that, so it gets complex.