Interesting stuff. FWIW, the "ichi-rei etc." formulation is found in some Shinto lines other than Oomoto (sorry, no references at hand -- later). For my money, what was original about Deguchi's presentation was the particular mix and dramatic presentation of a wide range of elements gathered from earlier traditions, rather than any particular innovation specific to Oomoto.
The comparison of the drawings near the close is particularly suggestive. I don't want to quibble, and perhaps my eyes aren't as reliable as they once were, but that single Katakana character in the center looks to me as if it is "Su" and not "Yu." But I'm not sure this possible variance has much effect on the totality of your presentation.
You may be right, I blew it up, but I can't tell in my scanned copy (although it looks like "Yu" to me it could really be either one) - in either case Ueshiba's cosmology "Su" pierces the void and moves to "U", which manifests as the two "In" and "Yo" opposing forces (added a note to the blog).