if it is written well, I have no issue with the casting. for example, I did not like the casting of capaldi early on, but they wrote the regeneration really well, and had him actually disliking the regeneration.
if they just have the doctor come in and be all "im a woman now, woohoo, deal with it" it will not go over well
if they just have the doctor come in and be all "im a woman now, woohoo, deal with it" it will not go over well