How about adding a "previous state" brush to LR? For instance, if the ambient light in a room is white balanced, then the strobe light is too cool on the subjects. It would be incredibly useful to apply an eraser brush to push the subjects to the previous history state (correct strobe white balance) before ambient light white balancing. The Temp/Tint brush is nice but I would like to control white balance values exactly via sampling and the combining of two history states. This would save time.