I thought about it, maybe I'll do that for some route endings. Not promising anything though.
Route endings.. booooo. Just make her do roleplay in some encounters with some dudes.
For example... "Guy: Oraoraora.. here i come. I make you pregnant" .. "Her: Oh yesh... come deep! Do it! Knock me up you big, forcefull dominant stud, you! (Shame i'm on the Pill and he can't get me pregnant ... but the thought is so Hot. Well... maybe one day i come back when i'm not taking them anymore.. fufufu) (or alternatively: Well Eve said it is difficult to get a Succubus pregnant the first time. My Womb has to get used to his Semen first.... damn... that thought is hot. Maybe i come back here regularely... fufu.)
It's not about her getting knocked up and end the game with a big belly.. just the theme, the possibility..cumplay. I said it in other threads... i find nothing more disappointing than sex ending "dry" without any mention of what the guy let loose when it is obvious he came. Also it's not about describing everything in detail... just subtle pokes and hints in that direction..some running here, some dripping there, her feeling it and realizing what it is and what it could do to her... the rest does the players mind.
Just wishfull thinking... nothing more
You do your thing and create YOUR vision of how the game should be.... you did an awesome job so far and i will play it even if it is more vanilla than my twisted mind would like.