I don't know. But I can tell you what my concerns would be. The Piezo disk is always going to have some pressure on it. You would have to have the ability to set or null that pressure so you can see when the nozzle is touching the bed. And then to further complicate things, you may need to have Piezo disks at every mounting point because the further you get away from a disk, when you press down, it is going to take more pressure for it to show up at the Piezo disks that are far away.

It is an interesting idea... But the micro-switch legs that kick down do work pretty well.