The problem with any adjustment is that he car can just pass from one view to another just between you refocus your eyes between them (ie. from rear to side mirror, from side mirror to side window).
The solution is panoramatic rear view mirror (you can see thru the rear plus backseat side windows) and side mirrors with curved section that pretty much eliminate the blind spot
>Researchers and engineers working on the GM Rear Camera Mirror have been awarded 10 patents – one for the streaming video mirror and nine for video processing. The patents cover innovations in the wide field of view camera image calibration, de-warping, glare reduction and camera hardware design.
I assume that this will add some friction to adoption of similar video mirrors by other automakers.
The solution is panoramatic rear view mirror (you can see thru the rear plus backseat side windows) and side mirrors with curved section that pretty much eliminate the blind spot