[Brightcolours]

If they made the optics (even) larger could they reduce the vignetting or is it a property of bending the light ? 

 

Do you think they went with a distagon design due to the 7's sensor (i.e, reduce corner incident light)  or did Sony fix that in the camera ?

 

Also it seems that mustache is not uncommon for zeiss (i.e, 21f2.8).

The light reduction in the corners will be partly due to the micro lenses of the FF sensor not being able to catch all the light at wide open wide angles, and due to the small back elements, which is forced on the designer due to the narrow E-mount. Making the front elements larger will not cure either..