I SHOULD keep my mouth shut, since you two are way above me in the food chain. However...
I would disagree that ki no nigare or flowing or come-to-hold or whatever you would call dynamic is cooperative in the sense that I get from your posts: that it is not 'real', there is no resistence or attempt to make nage make it work.
I believe that the reason uke moves in ki no nigare is to avoid losing connection with nage (a. because attack was after all the goal and b. to lose connection means to lose uke's own sense of timing and movement of nage, leaving uke open for an unpleasant surprise by nage), and to avoid stopping in a place that leaves them open to other attacks or techniques. They move because movement is life and the chance to gain the advantage and reverse nage, to stop and struggle is just trading blows and muscle strength.
I do think static/stationary training is important because it teaches the weak points in stregth and balance, and is easier for beginners because timing is not an issue. But since timing is important, dynamic training is also important.
I do think that it is important to realise that the techniques may not look the same, since one starts with a fairly well balanced uke and so other things may need to be done to unbalance uke initially, that would occur as part of leading him in dynamic.
Long winded, sorry, but I dislike a moving uke being referred to as cooperative rather than realistic. When I get an uke that likes to make sure he is always balanced and takes at most one step (usually looses connection almost as soon as it is made) I stop once I am out of their reach--even if the technique has not been done---and just smile at them. Usually by the fourth time they are motivated to actually move to get me. Some blackbelts I know will do a very unpleasant alternative technique with a value-added pin if uke looses connection. I think the reason Aikido works with a moving uke is not because the uke 'lets' it work, but because Aikido is working as it was designed.