Yeah, it's an interesting conversation for sure. I think there are mechanics and stories that can complement porn and sex in games, and others that really clash. I think fondly of Small on Top when I think of a nsfw game whose atmosphere and presentation I really enjoyed, Grove when I think of horny rpg battles where you fail deliberately to saddle yourself with sexy curses or see bad endings, Dormaus Valley for its terribly arousing scenarios and freedom in exploring them without ever worrying about losing progress, Strange Flesh when I think of a visual and gameplay marvel fusing action and sex in a nsfw game.
But stuff like obtuse puzzles, story drama for things or characters I am not invested in, or gods, resource grinding where I must use your awful fighting system to grind materials to progress or in another case -- spamclick my mouse into the ground gathering materials endlessly before spamclicking my way out of the random battle... are just really, out-of-place when my brain has shut down and I am playing to get a good time.
On your conundrum about mutations, I think pregnancy was a great way to go about things: limiting how many scenes you had to take into account by locking the other scouts until you gave birth, balanced with the sweet sweet fertilizing scenes and your birthing team entourage. Not every mutation needs special attention, maybe they could even only be tied to the individuals that mutate them. Also, there is at least one prostate milking scene I can think of, when you ask to be fucked on the way to the lightrot caves.
And oh no, Ophion appeared to work fine and does regenerate his lightrot supply daily. The problem was that if I changed my mind in the first encounter on whether or not I wanted to be experimented on, he would never give the option to change my mind again. (I just tested giving him a lightrot crystal after denying him the right to give me a puffy hole. Still nothing - he is one sulky titan)
And I can't wait! I've been checking in often to see if it dropped haha