For this to work we need a Z probe mounted to the hotend carriage. So we can probe at different points on the bed. Pretty much any Z sensor will work.

In theory I guess sensorless homing would work if you had it setup on Z. It will have the ability to probe different positions on the bed.

It is really just switches mounted to frames or gantries for Z that cause a problem here. Because they will always trigger at the same place no matter where X or Y is.

I have a video on Dual Z Auto Align with a BLTouch right here: (3) IDEX Dual Z Auto Align - YouTube

And a video with a $2 6-36v npn proximity sensor sourced from ebay right here: (3) Dual Z Auto Align Geeetech i3 Pro B - YouTube

While the first video clearly shows the BLtouch front and center, the second video is a bit harder to see the Z sensor as it is mounted on the backside of the extruder carriage. Here is picture of that Z sensor..



Hell a cheap old school 2 pin micro switch could very much work if we just mounted it to the hotend carriage and had it triggered by the surface of the bed.