P: Better auto stacking for bracketing, HDR, Focus Stacking and Panoramas

One thing that would be a big help would be for camera manufacturers to tag the bracketed shots, perhaps with an index number and maybe even an indication of what kind of bracketing is in use.  Then LR could accurately stack those bracketed shots.

This would not cover all cases, but then again neither can auto-stacking hope for that.   

Yes... and if the comparison doesn't work programmatically, then ask the user how many images are in each bracket. 

My background is image processing. The HDR really isn't that hard. They have metadata to work with. They can see sequential shots with specific exposure changes... 1 stop, 2/3 stop, 1/3 stop... LR already looks at this with the "Match Total Exposures". LR could further inspect the images for overlapping features. In fact, this would be very simple because they can find features in the first and then confine their search space in the successive images rather than running the entire array in the successive images. 

Panos would simply require a large kernel and quick pass rough feature matching.  

A combination of the above approaches wouldn't be significantly more difficult. 

@Rikk Auto stacking we are referring to, is not stacking when I manual processing the image but rather identify the images that should be stacked together to form an HDR image, a panoramic image (harder), a HDR panoramic image (much much harder), or a focus stack (again harder).

Might ask the user when type of auto stacks they are looking for.

Auto stacking for HDR should be rather simple, check change in exposure, in particular shutter speed, small time step between the end of the one image and the start of the next.  Look for groupings of 2, 3, 4, 5 with predictable set of changes in shutter speed.  Might even do a quick comparison of the images to assure that they overlap (or batch process).

Auto stacking for focus stacking and panoramic is harder but doable if overlaps are checked.