This is an interesting question, since I recently got a sort of mini-revelation when training under a Japanese 8th Dan who visited. He took apart our sword work and showed me how to do the basic bokken movements from the perspective of Ono Ha Itto Ryu. He was saying that the grip and striking techniques many of us use in Aiki-ken would not make sense if being viewed from the perspective of someone who knew how to use a sword and were really attacking, as it left too many openings for the Aikidoka to get off relatively easy technique. This, he said, may be good for Aikido practice, but not so good if we want to understand the basics of handling a sword.
Being one who emphasises effective technique, he showed us how to grip the bokken and execute the basic cuts Ono Ha Itto Ryu style and then show how the Aikido techniques should be applied (though modified very slightly to deal with the new grip and focus of the strikes) against this more effective, kenjutsu attack, instead of the attacks we normally use that make it easy to do Aikido technique against bokken.
I felt like a beginner at weapons work all over again, when I compare what we used to practice against what he had shown us, so I can now understand Craig's concept of mutation in what we often pass for good sword work in Aikido.
This of course has sprung a desire in me to learn Ono Ha Itto Ryu to get better insight into these principles and how they relate to Aikido. Of course, this ryu is also what S. Takeda studied and is also taught by one of the branches of Daito Ryu alongside the empty handed techniques if I'm not mistaken.