I suspect there is some "choice" (if not strategy) involved in crossing the line from just being a royal to becoming a celebrity. Some royals seek this status, maybe as an attempt to increase the popularity and thus the usefullness of the post?

I doubt that there would be much public interest in naked pictures of a royal, that are not considered celebraties. No interest, no photos, no paparrazi.

IMO, the lawsuit (another country and public air space) seems like a long-shot.