Oh, I like that last part! I wonder if Kyuubi would feel lest bloodthirsty without all the testosterone and other male hormones roaming around Naruto's body? Maybe enough that she could actually teach him some tricks, talk to him in his head, or any of the other things Kyuubi does in 'Friendly Kyuubi' fics. We know from Yamato's past that Orochimaru has knowlege of DNA, so I'm sure Tsunade does as well. So I can very well see her using a medical jutsu to trick Naruto's body into turning all Y-chromosomes into X-chromosomes!
Perhaps the Kyuubi would be like Inner Sakura and become Naruto's cheerleader. The Kyuubi seems to have some grudgeing respect for Naruto when he demands it to help him by lending its chakra (If i remember right its as hes thrown off the cliff). Could use the same scene or some other death immenant type of situation to get them to work together, if being female allows the Kyuubi to experience some of the outside world (sight, smell, touch, etc.) thrue Naruto it would go a long way toward building a working relationship between them. Even if it was unable to take over his body just being out of its prison (which looked pretty dismal and cramped) and free of what was likely close to sensory deprivation would do wonders for its disposition. Considering its relationship with Konoha it may play devils advocate when any one from the vilage wrongs him in some way (real or percieved by the fox) and encourage him to get back at them. Pranks then become a happy median between doing nothing and becoming a viscous terror. The Hokage then does nothing about the complaints knowing the possible consequenses of removing that avenue of 'justice' to Naruto and his passanger/partner.