I'm an author who has posted stories with PG and NC17 versions. I see no problems with this at all, provided there was consent between the author and the reader. However, I would be leery of an invisible pressure on the author to agree to edit her story (otherwise no one will record my fic) and of providing two fic options (PG and NC17) and only one podfic (PG). It would not be that hard to record both, actually, as the PG13 generally relies on the tried-and-true 'fade to black' after some kissing/making out *g* and is therefore simply shorter.

It's interesting your reasons for not wanting explicit content. I was thinking more of people who listen to fic in cars or living rooms, with other family members and friends around listening in *g*