There are a couple of options within GW's stable that you might want to consider:-
Firstly there's the
Sigmarite Sisters from Mordheim. Battle nuns. Ticks the boxes of Armoured & Female and are sufficiently religiously themed to scream CULTIST. Minor issue would be the posing, if you're approaching the Cultist problem the usual way and having them as IG, you might have a job getting some sensible posing with rifles from those models, but it's not impossible and is only an issue if they need rifles. Significant levels of re-posing will help in a way as it tends to allow more duplicate models to be used without the army becoming two dimentional.
Secondly there's the Mordheim
Amazons. I know there's not much in the way of armour but hear me out in this one....
At some point Slaanesh worship boils down to nudity (be it a pleasure cult forced to fight or a fundamental disregard for covering up), Amazons have that, well partial nudity at least. Combine that with feathers and strategically placed cloth, painted the right colours you can have a halcyon horde of warrior females.
They do have the same issues as the Sigmarites with posing required if you need them to have suitable equipment and the inevitable repeat models (this second issue can be off-set a little by rolling in the
Amazons from Blood Bowl) but again, even subtle reposing will allow a certain amount of duplications without becoming too samey.
Finally I must put in a word for Escher gangers. For my money, they are still some of the nicest miniatures GW have ever turned out.
Of the available models there are only four which have "big hair", there's three in the
top row and the other one is
far left, and in each case they can be changed very simply by means of a few simple cuts, and the colour their hair is painted really does affect how much you notice it anyway. The Spandex issue isn't a problem, once you get them close up you'll notice detail which suggests their clothes may be figure hugging but are far from skin tight.
Where they have a certain advantage over my other to suggestions is the obvious fact a good number of them are already hefting rifles which either are, could be fairly simply swapped out for or counted as Lasguns.
Another bonus, in my book, is the fact that a number of them have the spiked/studded stocking/chap type thing which is something of an oldschool
Slaaneshi theme.
Don't write them off till you've considered how you can alter them and how you're going to colour them.
