I'm currently playing around with modding the game's code in v28.1 to make the dildos function for the mouth.
It's not quite done yet, and I'm not really sure where I'm going with this, but it was surprisingly not that hard to
do this by combining the Fingering mouth code with the dildo code, and some minor edits. Like combining the
collision layer masks of the dildos and hand interact triggers. And adjusting the anchoring of the dildo to the head.
Edit: As far as why I don't consider it done... One is that I'm currently using a hard coded offset to align the dildo with the mouth, which doesn't work with every girl. And the other is that I want to factor this into the whole Fear/Arousal system thing the game has.