The closest you can get without really dicking around with dialogues is to have a breastless futa getting the blowjob, which a couple of dialogues suggest. Do that, grab a MILF dialogue, etc.
I'm intending to write one with a trappy little boy eating out his female teacher, but it's annoying to have to set up pleasure variables manually (because she's a futa without a penis, so only licking her "balls" will increase it) and it's just generally a pain to do.