More fun is anti-aiki. Not playing the Japanese game and stopping or stalling the possibility of it being used on you. These are not strategies or tactics they are body conditioning and rewiring. Some of which you then don't have to think about in use , others you choose to use.
And immovability is the source for all the other things that are highly mobile and retain the essence of the immovability in -your own- heightened and faster ...mobility. The central pivot is patently useless without the essence of immovability. And all the later fun stuff still starts with that building block. There are means and methods to putting this stuff together. Like most things you need to get 1.. before 2... then 3... and so on.
OK... it's a coincidence that we both used "sap your energy" (I said "sap the opponent's strength" but it's the same thing). But why does the opponent feel like his strength has been sapped? He pushes, but it goes nowhere and he can't apply any more strength it seems. What happens? (Incidentally, I already answered that question in a previous post, so I'm not just being rhetorical). Those are the kinds of details that will help beginners IF people are really interested in helping beginners and not just in grandstanding.
This idea of "secrets" that people are sworn to uphold, yada, yada, yada, is interesting to me, but frankly in this sort of "Baseline Skillset" discussion, I'm curious why such basic concepts are treated like some deep, dark koryu/masonic-lodge technology.
Your second-paragraph in the quote above is spot-on. That's where everything starts. Right there.