Making local masks or local corrections is not currently possible in RAW processing. But it occured to me that it would be relatively easy to assign a graduated mask over the entire image to apply a certain conversion setting for one side, and a different setting for the other side. if the gradation and rotation are adjustable, it would solve a lot of the local masking problems that photographers are faced with. What do others think?
If, in addition, the source image could be different for each side, and/or the grad mask is a blurred luminance mask of some sort (like shadow/highlight correction), then it could even become possible to do bracketed composition without resorting to PS...