I feel like going back to bare wood on a bathroom window would be an error on practicality grounds. It's also quite hard to strip it so it's completely clean.
This was my concern having sanded many an old sash window just to key it for repainting.... having seen the links Tenderloin shared above I'm far more comfortable with the idea that it can work as is, either refreshed in white or maybe even something more daring.
I feel like going back to bare wood on a bathroom window would be an error on practicality grounds. It's also quite hard to strip it so it's completely clean.