This conversation has been merged. Please reference the main conversation: Camera Raw: Ability to permanently crop an image for smaller raw file sizes
Images which are not so important that I want to save the huge RAW, I would like to convert to compressed DNG. The rotation and cropping should be applied though - this would reduce the file size for certain images a lot and even provide better quality for the rotation. It would also make sense to optionally downscale the images (unless they are already cropped). I could imaging it would make sense to uniformly select a resolution of 8,12,16,20,24 megapixels, if I already know, that this images will be never be printed "huge".
Yes, I can do this all with an export to JPEG, but there the WB setting is applied.
Smartpreviews provide some of the features mentioned above, but their resolution and compression can not be customized and they are stored at an anonymous subfolder, similar to any other cache file. So they just mean that the technology is there, but cannot be directly utilized.
I hope such a feature makes it into LightRoom 6