The problem comes in that not everyone is comfortable playing female roles, iridum (me, not gonna lie, lol). But that's why I only left two Houses open initially; Karandras and Fetear, to funnel a number of players into a united situation. If necessary, it could be narrowed down to one House as well, though if it did, I'd want it to be Fetear because of my character.
As for plot, that was pretty much the idea; House machinations, both in-family politics and plotting against other Houses. Other Houses would be used by me to generate plot movement when necessary, or to respond to the plots of other PC Matron Mothers. Meanwhile, the sexual aspects of the roleplay would be mostly one of two themes: priestesses taking what they want from males, or males trying to turn the tables. Dominant males either don't want to be here, or need to be willing to play their cards right with the right females. Essentially, this is almost like a drow soap, with drow living their normal lives of plotting, scheming, killing, and hot sex.