I do believe "authentic" watermarks would help a lot. They will have to be locked to a lot of details about the file, you will not be able to color correct, resize, crop, or change the compression method. Probably allow cutting movies between frames however. Some one-way writing of the watermark is put into the camera, with the decoding key/result added to a database that does anything it can to insure only actual cameras are registered.
Watermarks people want to be remove can be made much harder by making the test for the watermark much more expensive, slow, and/or locked down so only authorized users can run it. Videos detected with the watermark are remembered so any similar-enough video also acts like it has the watermark, even if it has been manipulated enough to remove it. It also has to be very hard to create the watermark by anybody other than the registered creator so people can't use this to reject real videos.