what would be the characteristics of, and your criteria for, a feminine mod? i'm definitely intrigued and wonder what it would like.
batteries, tubes, atomizers, are all phallic...some perhaps more aggressively so than others. i guess a box mod or on the extreme end a commercial vaporizing machine, while not exactly yonic, would decrease the phallicism. if it were just size, there are different mods, and if it's color there's variety in that department as well. from a glance the provape looks like it's ribbed for "her" pleasure, though it's probably that more men are holding it. is it something that should arouse the senses; is it sexual, or anti-sexual in the sense that it should disavow a masculinist heteronormativity; should it have androgynous aesthetics?
put it out there, and someone will build it!