I know that the cheerleader one has been done, I don't think it got very far but certainly something's been done with that one can't remember who did that though.
As you can probably tell by my stories so far, I like role reversal so potentially we could do one where Jon and his male friends become cheerleaders and Karyn and her friend (or even Sarah) become football players, I also like to keep it where they don't change physically; just the way they dress, act and are treated. I would like to keep this for anny other stories as well if you don't mind.
Playboys could be interesting, or we could have hooters waitresses with girls becoming bouncers or something. The stewardesses would also be good (do they have to japanese?) and we could have female pilots. And again in the hospital we could have male nurses and female doctors.
You must have lots of suggetions then :)