If you are going to chop retrobolted mixed routes en masse, please just check that the original gear placements are still in tact where the new bolts are.
I have personally seen gear placements erode to the point where thay are unusable and nothing else exists in the vicinity. Sure you could argue that those routes then should just be climbed as is, but the nature of climbing in the blueys is that no-one ever adjusts grades for holds dissappearing, placements blowing out or bolts being added. once you walk the path of modernising or demodernising then the appropriate notification has to occur. You cannot always see the evolution from the ground.