What about some sort of miniature spark erosion machine. The trick would be to make a tool for the z axis where the wire does not have to pass through the work piece. This way, you could do multiple passes to make your cut instead of a continuous full-depth cut. Imagine the super edge finish you could get! The kerf might have to be fairly wide to get a strong enough tool but there would be no actual cutting force on the tool. Just an idea, carry on
