Originally Posted by Fraser
A bit like the nikons with the electronic rangefinder that can still be adjusted even when using a mf lens.
True, but one is still adjusting the Nikon AF system's calibration.
The green dot's behavior is affected by AF micro-focus parameters. Of course there's no way to mechanically change the focus without human intervention. The only difference is a person moves the lens barrel based on the green dot feedback.
I think it would be awkward to implement the same sort of sei-automatic lens specific focus calibration with a mechanical, optical RF. In principle one could replace the mechanical RF focus adjustment screws with micro-electrical servomotors. Then adjustment parameters could be stored in-camera.
In practice I suspect the servomotprs might be too large to maintain the M body shape and very few customers would be interested in paying for the R&D and manufacturing costs.