My own feeling about fencing is that distance and timing are permently linked, and you can't teach one without the other. Given that consideration, I agree that if I had to teach one thing, distance/timing (tempo, in my language) would be the primary skill.
But, remember, this skill is permently linked to the others. You can't manipulate distance without a mechanism, and that mechanism is footwork. Technical failures in footwork and bladework always impact distance and timing. All these skills have to be brought along together.
If I have to make a choice with a student when I'm teaching in what to emphasize, then, yes, control and manipulation of timeing/distance is what I start with. I'm willing to sacrifice SOME blade action/technical skills to teach a concept, first.
