Very interesting post, thanks!
For example, certain versions of kokyu-ho seem incredibly unrealistic unless the guy continued to hold your hand throughout the movement. This is obviously ridiculous in a real life situation.
Why is this obviously ridiculous? Did you try it out?
They grab your wrist, you take their balance and keep them unbalanced throughout the technique. I think most people will hold on to your wrist. And if they do let go, they're in a disadvantageous position, giving you a chance to adapt and do something else.
Of course, in self-defense situations short techniques are preferable. The only reason I see to do something elaborate is if you need to keep adapting to what the other guy is doing, but I'd rather call that a chain of simple techniques than one elaborate technique.