That would change the piece so completely. It is an artistic nude, one designed to show the beauty, form, and function of the human body. Yes, your idea is quite wonderful, but a thoroughly different purpose and genre. And I find the belly button ring to be a nice modern tweak, to show that classic beauty and style can still be demonstrated by a wholly modern woman.
And I also hope you do not take offense. I can totally see your idea as the basis of a lovely romantic piece, but hope you can see another perspective as well.