I'm sure this topic has been debated at length, but
...Personally, I'm quite open-minded about the prospect. Especially if it's the delightful Hayley Atwell!
U know what I'm saying? 
But on the other hand, I don't know whether it's strictly necessary either.
Afterall, I think of the female lead as the Doctor's female (if human) equal who displays equal measures of heroism in the show as a counterpoint to the male protagonist. So that covers anyone interested in gender equality about girls doing anything a boy can do!
Besides, I envisage negative headlines by a braying press if they cast a female Doctor: "Ailing BBC1 sci-fi takes a punt & reboots with a female Doctor for the first time ever!"
"Critics say NO!" What do you say? 
"Critics say NO!" What do you say? 




