I think there was a movie where Sherlock Holmes was a woman. Can’t recall if it was period set or modern times. Might have been a tv movie or a pilot though.
Well, the show Elementary did this with DR Watson, I presume this is what you are remembering?
When I first saw this show I thought it was being done for the same reasons that warbler seems to think the DR who thing is. But since then I picked this show up again and really enjoy it.