I've been tossing this around in my head for the last few days and I was wondering if you'd be willing to expand on this a little.
Was your remark about internal shape meant to describe the non-rigid quality (e.g. I know "posture" often implies a non-moving form) of the internal workings?
Also, what do you mean by intent here?
I think I wrote some sort of similar explanation on A.W. a few years ago, but I have no idea where it is. I can give you a *rough* idea, but let me emphasize that it's an incomplete idea and there's more to it:
Stand upright, feet about shoulder or a little-more width. Let a partner push into (and very slightly downward) your right should and you try to relax, let the left leg compress from the push, and the left foot should be the resting place for the push. Naturally the body "structure" is what conveys the push down to the foot, but in this case the "structure" is standing in for something I can't tell you quite how to do in writing.
Then have the partner stop pushing and walk around and push on the left should, all the same thing, etc., so that the push winds up in the right foot. Try not to move any part of your body in between the pushes. Just first accept the push into the left foot from the right shoulder and then accept the push into the right foot from the left shoulder. You can feel that there has to be a minor re-arrangement inside the body to accomodate the force coming from the different directions and you kind of "set up" in order get ready for the push from different sides. That "setting up" is done via "intention". If you learn to hit, push, receive-forces, manipulate, etc., this kind of intention path of strength to and from the ground, your skills will increase. But since you don't have to move to do these intention changes, there really is no "shape". I can lay on the ground and mentally change where and what direction forces are going through my body. I can lean over into odd positions and manipulate these same kinds of forces. So it's not "shape"; it's intention.
When Ueshiba let the Sumo wrestler push on him, Ueshiba responded by meeting the Sumo wrestler's force with a force that Ueshiba arranged mentally. That force "blended" with the Sumo wrestler's push and negated the push. So Ueshiba used the "Divine Will"... and he called it the secret of Aikido. Of course other arts use these force/ki/kokyu/jin skill manipulations, too, as part of "blending", hitting (atemi), and so on. There are more extensive discussions about these skills on QiJin, if the above didn't answer your questions.