There is no good reason for the Doctor (Doctor Who) to regenerate as a woman.

1. "Character Focus." Not true. The best candidate would be Jenny, who is already a Time Lady and still very young as of her last appearance (despite being physically an adult). Bringing her back would also allow the Doctor to be a father-figure again, which hasn't been explored since the classic series and is a far better use of his character. Your argument about people debating which Time Lord is the best is flawed for a simple reason - the Doctor is the show's main character. As long as any Time Ladies remain companions rather than trying to usurp the Doctor's role, there will not be a problem. 2. "Blind Casting." I didn't make my meaning clear. "The Queen" refers to the present-day Elizabeth II of the United Kingdom, unless otherwise stated or you're from a country that has its own monarchy. My apologies for assuming you'd know that. Obviously a fictitious monarch can be portrayed by anybody you like. Argument from tradition? BOP is on you to prove that the tradition needs to change (says so in the rules). The Doctor works fine as a man, you have to provide a good reason for making him a woman. 3. "Fan Interest." If you had actually read the TvTropes article I linked you, particularly the examples, you would see that the rule applies outside of anime as well (they even have a drop-down called "Real Life"). The name just means the rule originated in anime and then applied elsewhere. As both you and the voters are capable of READING, I don't need to go into this any further. Comics aren't canon to the TV series, so they're not precedent. 4. "Fun." Fooling enemies with a gender swap would be funny and entertaining the first time, but becomes boring every time after. And not to sound all touchy-feely and politically correct, but changing the Doctor's gender for a one-off gag is insulting to both women and trans people. The Doctor changing his gender would upset families. Having him hook up with Jack would just get the show cancelled. Also, you are confusing physical sex with sexual orientation (and with gender identity for that matter). Just because the Doctor regenerates into a woman doesn't mean he'll like guys or think of himself as a girl. That too is insulting to trans people and gays. The flirting between the Doctor and Jack was played for laughs because it wasn't serious, and that's the way to avoid offending people. 5. It's offensive. By regenerating the Doctor as a woman, you offend those with conservative/old-fashioned values. By addressing sexual matters in a show that children watch, you will offend parents and moral guardians (not to mention screw those kids up big time). If the Doctor is unhappy with changing gender, you will offend trans people. If he adapts to the change really easily and starts behaving like a woman, it will come across as sexist and cliche. The gender swap will also change how the fans relate to the character, and potentially put them off the show. There is simply no way to change the Doctor's gender without upsetting most of the viewers. And before you say "they can adapt", it would be easier for the few extremists who want a female Doctor to adapt - or just stop watching entirely if having a white, British male in the role offends them so much. And just to remind you yet again, BOP is on you. You're the one wanting to change the status quo, so you have to give good reasons. If your reasons aren't good enough, you lose. All I have to do is debunk your arguments.