I've seen two productions of Pippin with a female leading player. One she sang it in the guys octave as an alto, and it was somewhat awkward. The other sang the entire thing up the octave in her crazy belt range, and while it was an amazing showcase for this girls ridiculous belt, everything was blaring and words were missed. If a girl were to do the show I would want the keys changed to one that would befit a girl's voice better. There's definitely a different dynamic when a guy plays it verses a girl, but with that casting you have to rely on the director to tailor the feel of the show to whoever's playing each role.
The original concept for the Leading Player was to be played as an old man, but when Bob Fosse saw Ben Vereen for the part he changed the entire concept to a coniving, young, sexy man.
Eeeeeeyyyyyyyyaaaaaaaannnnnddddd aaaaaaaiiiiiiiiyyyyyyaaaaaammmmmmmm teeeeeeeelllllliiiiiinnngg yyyyooooooouuuuuuuwwwaaaahh...