Alexander Siddig is an actor I hadn't considered, but the more I think of it, the more I think he would be ideal. He's not a well-known actor, and he has the acting chops to do the role justice. Idris Elba may be banded about, but honestly I think he has too big a career, he's spent a long time building up his resume, and I don't think the BBC will be able to let him have enough time off to pursue the other roles he would enjoy, and Luther is still very successful.
As to a woman, while many of us fans may accept it, we aren't the people the BBC are aiming for.
If a woman becomes the Doctor, how many eight year old boys will be running around the playground with the new sonic, shouting "I'm the Doctor?"