When I think of corrupt powerful woman and Whedon, I automatically think of Lilah from Angel. Not that Stephanie Romanov isn't attractive, but she's not dripping in leather and makeup.

I'd love to see an evil female character who is genuinely gross (like, a zombie or something(*)) do the whole "creepy touching" thing

Isn't this the traditional crone stereotype? The evil witch, corrupted by her own power, thinks she can titilate the 'hero'?
Also, lol Spn and sexual stereotypes. I mean, wow, lol.