The closest game I'm aware of that lets you toy with and stretch characters dynamically is Hotel Elera, but that still has prefab positions.
You just reminded me. There is an insane recommendation I can give just for the hell of it, based on "toy with and stretch characters dynamically".
KoboldKare. Yes, that game.
The Kobold beasts are freaky toy animals by their anatomy. You can breed them for bigger cocks, tits, and bodyweight, sure, but the real magic is their wormhole nature bodies - if a cock is long enough to go in through the ass and come out the mouth, it will happen. The other way around too. Through a whole kobold's body into another kobold's body, sure. Even into the same kobold again, that's ass-to-mouth autofellatio. It's all nonsense for the purpose of breeding more kobolds. Go ahead, use a literal damn pump to swell a kobold's belly to massive size so it lays a massive egg. Heck, sodomize a kobold to orgasm using a dildo, another kobold, or the egg it just laid. Whatever. Just having them stand next to each other in certain positions makes their cocks gravitate into a hole and you get autoimpregnation just from them idling standing next to each other.
Anyway hard to say the game's good, but it's so bizarre it'll feel good for a while.
Also we need to stop talking recommendations, it's been a while and that's derailing the thread against forum policy.