Why do I expect that there would be a minisong (possibly used as part of "Got a Little Gift") that would sound suspiciously similar to Marvin Gaye's "Let's Get It On" for Sarah's flashback to her and Peter's first time together?
Also, I'm somehow imagining every single sex scene being done, to some degree, in the style of Grand Opera, where, as Anna Russell put it, "You can do ANYTHING, so long as you SING it." So yeah, full-on unsimulated sex scenes... with the participants singing about what they're feeling the whole time. (Now THAT'S acting!

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...now that I think of it, that could actually be *really* interesting, to be honest, with many different contrasting musical styles as moods change, intermeshing beautifully. (Imagine, for example, when Butch tries to rape Peter, how each would be singing something VERY different, with Peter's being fear and horror with a *hint* of arousal--she IS physically attractive, and he IS an 18-year-old male, so there would be an undertone there along with the shock, fear, horror, and helplessness--while Butch's would start as a combination of arousal and triumph that would then slide into shock and horror at what she's doing before she bails out. Doing this all in a single, cohesive duet that gets across the feelings? That's the sort of thing that a composer would consider a masterwork, right there!)
The one thing I'd say, though, is that you'd need to make sure that Sarahwuff doesn't have songs, per se, at least until she gets enough control to be able to start speaking (even a little) in wuff form, to avoid the sort of disconnect you get in Rocky Horror where Rocky is introduced with a great song ("Sword of Damocles"), but then never really speaks in any form but some grunts for the rest of the show. She might have music, but it'd have to be either instrumental, or just have wuff-noises as lyrics to make it less jarring that she doesn't speak in wuff mode for the majority of the show. (That said, having human-Sarah's actress follow Sarahwuff around and sing *her* thoughts, as a stage version of the "chibi-Sarah on the wuff's shoulder" trope, would be a way around that...)
I don't suffer from insanity; I enjoy every minute of it.