Yeah, funny thing, there wasn't much windings, central pivot, upper cross, etc. going on during my yondan test. I probably had slightly better central equilibrium -which was not much to speak of- than the attackers in general (because they were attacking in that aikido way). I'm confident that by godan that will all change.
Of course I will see the relationship to what I am focusing my personal practice on to what I am teaching even if it is hidden a bit. I am just looking for inspiration on really obvious ones for teaching purposes. I want to try to make the aiki to waza relationship so obvious to my students that I don't have to explain much verbally.
So in the example I provided, if I start the class off working the a solo exercise with the upper cross highlighted in it, and then do that kokyu nage with your arms sticking out to the sides, you'd have to be pretty thick to not get the connection. I can't think of too many other techniques/waza where I hold my arms out to the sides most of the time, for instance.
Tenchi nage can demonstrate central pivot very well. I think I need to just teach kokyunages for a while and look for the connection in reverse, and then hightlight them in the subsequent classes.
As far as live vrs dummy - this may not be too popular, but I don't think it matters too much in general for this point. I'm thinking that typical aikido waza works as an expression of aiki if uke attacks with external power and the nage role is really someone with internal power receiving (being uke himself). My opinion - dummy attacker or alive - the power differential should be sufficient for that to not matter too much. (If someone wants to debate this, can we do it in a different thread? I'm sick to death of aliveness debates.)
When uke has aiki too, the whole ball game changes and I don't think anyone really knows what aikido will look like at that point. (But it will be fun to find out.)