I think what Michael is saying is, all the kokyu in the world is not going to keep a sword from cutting you, but movement will. Further, when using a sword, one doesn't need much force to make it destroy a human body.
Aiki is built in the body, yes. But that doesn't mean one is invincible. It'd be like having aiki and using it to stop a bullet. Kind of silly.
However, if each person has a sword, then the one with aiki has an enormous advantage. The sword is merely an extension of the body, right?
High ranking kendo people studying under Ueshiba for "tai sabaki", and that didn't just mean how to move physically.
As Budd stated, once you get aiki in the body, you work on aiki with weapons as extensions of the body.
Or vice versa. Maybe it was Takeda's work with sword and spear that instilled aiki to a high quality in him? After all, it's much harder to get aiki out to the tip of a sword or spear.
EDIT: Forgot to add, yes, movement is important! I definitely agree.