I seriously doubt GW was considering female wargamers when they were designing SoB.
I've never really believed the make them in plastic and people will buy them line. They didn't really sell well when pretty much everything was metal they were first released in 2nd ed after all. Still they haven't done it so we don't really know.
Would they come over better as their original incarnation as a force used to persecute rebel Astartes? I don't know they just feel a little inconsequential at the moment I feel they need a better job than just guarding temples.
It's all a bit of a vicious circle low sale equals low support which in turn means low sales. Still GW seems more inclined to take a few risks at the mo so who knows? The Sisters of Silence (who are way cooler) will probably go over well and that may kickstart things.