The novel you linked to has already been written, and doesnt need to be redone on an erotic scale. Nannys/babysitters, cuckqueening, and female takeovers can be interesting, and in all but the most basic facets are underrepresented (particularly with the interloper stealing away children and other life-defining female roles as well as merely the standard - seducing the husband). That's something very complicated and layered to explore, and is in a somewhat similar vein. You don't want to get more similar than that here, I doubt.
