The Doctor's never been a particularly masculine or "manly" character to begin with, so I don't really see how giving him boobs would make much of a difference.
It would still be essentially the same personality and same character we'd be watching.
It really doesn't matter how 'masculine' The Doctor is or isn't. There are no character traits that cannot be portrayed by a capable actor of either gender. Hell, Starbuck was way more 'manly' than Apollo and that didn't hurt the believability of her character one iota.
Some say that, of all the souls he has encountered in his travels, his was the most human.
know is, we've lost a legend.
Goodbye Leonard Nimoy.