As thoughts on future pregnancy options. In itself, fertilization and subsequent pregnancy is good, but the interest of this option increases at times when the game implements the mechanism of a random chance of conception. Roughly speaking, you can have several opportunities to conceive with the same character if you meet him more than once in the story, or you can even have only one chance in the whole game. A lot of interesting things can be built around this mechanism, increasing the value of the reproductive possibilities of both the main character and his partners. By the way, it would be nice to throw the guy into some colony as a male inseminator
p.s. On the other hand, I understand that it's one thing to get high on powerful rendering and story creation, and quite another to fool around with renpy codes, turning a virtual novel into a full-fledged interactive game.