i believed one of the problem with using structure alignment to resist a push is the power of the push pins your body in place, which is not good if you want to be mobile afterward, as the push continues. as Hunter mentioned, structure alignment will fail with sufficient force, but that's the next stage. resisting a simple direction push is only part of the requirement, but we need to understand the bigger picture of this which includes mobility, manage increasing load, and multiple directional forces. so what we do for a simple directional push must fit into the larger picture later. we can't just do one thing for this and use different set of respond for others. see Vlad comment (second hand) in this post http://www.aikiweb.com/forums/showpo...31&postcount=2
I agree, there are lot's of problems with using structural alignment to deal with force. The reasons you sighted are good ones.
But my question is, what else can you do? How can you better deal with strong force coming in? The way I described is the best way I know how (within the confines of 'taking' the force). If there is another way, what is that way?