Oh, but to give you some less-grandiose ideas, one way I thought of to have the late-game be less "spam nails until you get to 100" would be something along the lines of "sensitization pins", which wouldn't do any arousal on their own, but would increase the power of clicks/pins in an area around them (0r maybe just the whole doll? So as to not incentivize people to place all their pins in the exact same spot. ). And also, you could make the orgasms with at least one nail in count as two? They seem like they're strong enough to count for more than one. And that'd let you end the game at a "lower number" without actually having it not end at 100.
And, for the visual aspect of sensitization pins, they could make the nipples even harder when enough are placed near/on them. And do the same for the clit, too, perhaps? That doesn't seem like it'd be too much work to add, in terms of conflicts with the base wetness progression.
I imagine you might get them (in this version of the game without a shop) by trading in some number of your basic pins. Maybe 5? I suggest this because having to put all your pins back in after using a nail becomes a major pain later on, or at least it would if nail spamming wasn't the objectively correct way to go in the late game. So if you decide you want to "fix" that and change up the late game, this would be a pretty good way to do it.
Another way to "fix" the endgame that I thought of could implement the "edging" that we mentioned before. Maybe successfully edging her would permanently increase her sensitivity? That would counteract the much higher arousal required (or, decreased arousal gained? It's hard to know when it's measured in percents) for the final stages. But, that would require a way to remove all pins without adding a nail, so as to stop all stimulation when on the edge. You could just make it so that nails themselves are manually removable, that way you could: add a nail to remove the normal pins, then remove the nail itself. But importantly, it'd add a mechanic that would need a tutorial in a notably tutorial-free game.