Re: static vs. dynamic waza
When I first started teaching, I got the difficult class where only like 3 students who didn't know Aikido would show up. I never had a good uke to use. Every time I started a technique the uke would give the wrong energy, often ending in disaster.
So I started letting the uke pick the technique I would do. I would not say what the technique was, have him grab, katate or what ever, start my technique, and whatever his response was, I'd go with it and that would be what we did next.
It worked out really well, and taught me that what nage does is dependent on uke's response instead of the other way around. I used to think that my technique had to be so solid that there was no resisting it. Then I realized that it works much better (and is more realistic) to change based on the attacker.