This is a story I wrote for a contest on another site. What I've tried to do is introduce a premise that could actually work in the Real World, and extend it to include the usual elements of erotica. There really are such "Daredevil" clubs, and there are masturbation clubs, so I think that mutual masturbation in an adventure-club setting would be entirely workable. Since most men masturbate, and most adventurous women do, too, why not get them together in an environment where they can watch each other do it, without fear of pregnancy, or of being rejected as a sexual partner, or of proving to be disappointing as a sexual partner?
The other element of the story, of course, is having kindred souls, with kindred hang-ups about their imperfect bodies, getting together. It's the old "you can't judge a book by its cover" story, with the addition that we often judge ourselves by our own "covers" ... the bodies we have ... and short-change ourselves in the process.