I mean hyperthetically I dont see why an angel-spirit couldnt do a similar possession ritual as the Succubus. As long as the sacrifice is tight & Wetesh has enough energy/an amplifier of some kind then someone like Ziva or Oksana could possibly become mother host to an angelic daughter (Houri, Nephilim, Cupid/Eros whatever u wanna call her). Being a servant of Wetesh the angel would be an innocently sexual, free-spirited being.
I could imagine an amplifier artifact mixed with an orgy (with 3/4 or more acolytes involved) in order to bring the being into existence. I mean according to Tinkerer the only difference between Angels & Demons in this world is apperance, temperament & morality (I feel their closer to the Fade Demons/Spirits of Dragon Age in this manner).