Now, let's ignore for a moment the limitations of the system itself (only applies to Facebook ecosystem, seems trivial to bypass, only works if the potential victim has advanced knowledge that someone wants to post picture of them etc.).
The system will increase the risk for everyone else, by introducing new threat vectors. How long do you think it will be until we see phishing emails and fake FB "upload your nudes here" sites? How many abusive partners (or just pranksters) will make their partners think they have nude photos of them, just to make them go through the indignity of photographing themselves nudes and uploading their pictures.
Furthermore, don't forget that the victims will have to take their pictures with their phones or cameras. Which often sync said pictures with PCs, NAS, clouds etc. - sometimes even without their owners realizing. So you end up with a lot more attack points from which the nude pictures can be leaked or stolen.
You solve the potential problem of some, by creating a bigger problem for more people. I'm not seeing this as an improvement.
Risk Transfer is an acceptable risk mitigation strategy only if the parties to which you're transferring the risk to are cognizant of it, and able to accept it.