I got dragged into watching Thor: the Dark World last night. Suffice it to say that even 12-year olds see this film mostly as an opportunity for cynical hilarity. And anyone watching it could be forgiven for supposing that Thor was originally the Norse god of testosterone, with all that thunder-god business as mere decoration.
So I'm kind of curious about Marvels idea of making Thor a woman. Their narrative for how this will happen is simple and perfectly justifiable: they treat Thor as a title instead of a given name. As such, the role can be embodied by anyone worthy enough to hold the 'Thor Hammer', as implied (sort of) by the hammer's inscription. Apart from vaguely wondering why they didn't pick an already female mythological character to work on, whether they're going to make the new Thor look like Armoured Barbie, and whether she's going to use nubile male characters to signal her power and status as Marvel's male characters continue to use women (and if not, how will she?) there is no problem with this narrative ploy.
In Scandinavian mythology, Thor's gender was far from fluid, despite the notorious occasion when he most unwillingly dresses as a bride to get his hammer back from Thrymr, king of the jotnar. Loki, on the other hand has very fluid gender, sometimes appearing as an old woman, or giving birth to the horse Sleipnir which 'he' conceived in the form of a mare. The bride stunt was his idea! But then Loki is a trickster god, who blurs other categories as well: truth and fasehood, good and evil... He's supremely powerful, but untrustworthy, necessary but unlikeable, just too damn complex for simple, straightforward gods like Thor (though I think he's great!). At any rate the original Scandinavian myths reveal the insecurities of their makers when it came to blurred gender roles. Rather like some of their modern day successors.