Instead of making the Doctor a woman, why not just make one of the other Time Lords escape Gallifrey's pocket dimension and have that one be female? Not every iconic male role has to be transformed into a woman/gay because "it's hip, it's trendy, OMG we're so with the times!"
But imagine Capaldi regenerates into Tilda Swilton and she is like " OMG !!!! I AM .....a GINGER !!! =D"
