You know i don't know for sure if it's been asked or if anyone's thought of this before but, will there be pregnancy or impregnation in the game? Now i understand for story reasons why that seems like it might not work as well...Magic.
And for most characters yes i'd agree. Over 90% of the characters i think this would make zero sense with. But there is a way to implement it that we can thank the recent updates for that makes perfect sense and in line with the character.
Namely, going to explain how it could work before getting into the specific character, it could be made so that only very specific characters would have the feature be a part of them. These characters could be the only ones to have pregnancy linked to them and it could possibly be linked to a non standard game over if the dev's so choose. Much like how there is one for not finding harry early on when Ginny is controlled into attacking him as a girl.
Now i wouldn't say that the player character themselves could or should get pregnant as a girl. Though that is only in this case and an argument could be made. But rather in this one i am writing here, it is that they can get specific girls pregnant, as long as it fits their characters to a point to either want that, or think to want that. And they obliviously have the necessary dick to do so, requiring tonk's questline with it for a girl or just to be male.
Now with that addressed, I girl I would say is most useful for this or perhaps makes the most sense is obviously Lavender Brown. Of all the girls, or even characters written, she's the most obsessive of them all and clearly willing to go to lengths to stay the player characters girlfriend if allowed to be so. As well she mentions wanting to marry them and so on quite quickly after having sex.
With that in mind it's somewhat in character for her to actually try or think to get herself pregnant to try to make sure her and the player character stay together and that this could be the best way for it. Sticking with her character, it could only occur to her to try this if a player does certain things what those are, are equally simple.
The player must get the quest to break up with her or try to break up with her enouph to get it, so that she stupify's them/freezes them in place. After this she could get the idea to get pregnant to make sure they dont' break up. So while the player is looking for a way to get her to break up with them, before or after finding out about the potion, there could be two ways to handle it.
1. Lavender comes to the player this time around at some point during the day and wants to apologize for using her magic on them and offers to make up for it so to speak with sex. Agreeing to this of course leads to this, either by going to the normal place in the evening or hogsmede. Weather or not this is a new position with new art is at others disclosure. But her dialouge would mention several times wanting to feel the players love inside her. There could be a choice to pull out of her or not. Finishing inside her would result in pregnancy and she would tell them later the next day or two.
2.The player more simply has sex with her before giving her the anti love potion. This would be the normal scenes as they are in game, which are quite good in my opinion, but would linger on her after the creampie for longer. So long as the player has a penis of course and her commenting on it.
The result in either case is the same. WHen the player goes to give her the potion to drink she tells them that she is pregnant, shocking them and leading to a non standard/early game over with her. Though possilby an extra pregnant sex scene with her, with the player possibly commenting it's not so bad being with her.
The way to avoid it is simple. Don't have sex with her in case 2. Or decline her offer in 1, though she will push and try to insist which would hint new players that they probibly shouldn't have sex with her as it may be a bad idea.
And that is one way to implement the feature, just using lavender brown as an example. What do all of you think?