I wish I lived in a world where adding that kind of customization to a game was trivial, or even just tedious.
I know you (and others) will see it as maybe dismissive, but go try and make a 10 second looping animation using 3D models colliding with each other in blender for example, now try to recreate that same animation with 3D models colliding but make it so the model can have a range of multiple variables, try to make that animation look as good as the 1st one from every angle. No clipping, no physics explosions, and properly aligned.
That shit is no small task, especially for porn games which are typically made by small teams or even in some cases 1 person.
I'm a big proponent of customization and player choice in games, but when it comes to games like this one which are very clearly and very obviously going for a specific look and theme, it's really not reasonable. It would be like complaining about not being able to play as a custom male character in Tomb Raider, or not being able to play as a custom female character in the witcher.