1.) I believe its all but confirmed it will be PG-13, I recall it being stated that the creators refused to compromise on setting, tone & style but conceded with Scar Jo & the rating so the studio would be able to sell the film & it actually make money.
2.) She did in Under the Skin but that was of course more of art film.
I would say it is in part essential to its iconic-ness.
The opening credits of the 95 film playing over her body being built is absolutely beautiful. (incredible score helps immensely also)
I have yet to watch the various follow up series or movies but from what I have seen she looks far more generic in them then in the manga or the 95 film.
Never minding titillation her being near naked, turning invisible & kicking utter ass was something truly iconic & awesome to behold. And said follow up material has treated it like a bastard step child out of prude cowardice.
1.) Good luck with that.
2.) She doesn't need to be, in the 95 film I got the impression she was given a standard issued female body, hence during the montage with her on the boat she sees someone with the same body through the windows of the restaurant above her.