I wonder if is possible with some firmware using 2 end stop's on separate Z motor (aka Z_DUAL_ENDSTOPS in Marlin FW) for G28 and using a sensor (inductive or whatever) con extruder block when using G29.
If some one already did that can just share the info or a link.
(I prefer to ask before change some code)
Tyvm

Did you have a particular firmware or electronics board in mind?

It's possible to use dual Z endstop switches in RepRapFirmware too. However, the recommended approach is to use the Z probe to level the bed by adjusting the leadscrews independently instead. See [duet3d.com]. After that you can use G29 to do mesh bed compensation too if you wish.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Usually, i work with ramps 1.4 and marlin for prototyping and experimenting, but can use also other firmware.
I will check in the code, must be not difficult to adapt if is not possible just by configuration and i post here results

#define Z_MIN_PROBE_USES_Z_MIN_ENDSTOP_PIN

//#define Z_MIN_PROBE_ENDSTOP


should invert commenting on those line maybe?