I Think if a user is asking for deletion for one or two image's with good reassons the image can be deleted. But without very good reasson the image should stay.
for the second part. If a user ask to remove all image's because he is not the maker. We should block the user for ever. But he released the image's under a licence. He is the one getting in trouble not wmf. The image should be kept when they are used.
Houdoe, Huib Also now as SterkeBak