Sadly, no one has been able to export their sims as an mesh. It's because EA saves your sim's slider values, rather than the mesh. So basically, when you would share a sim with another person, you're actually exporting some data files like slider values and a lot of number-related things.
I have tried ripping it with ninjaripper (and another ripper) but it's not worth your time. It will export the default sims face, not your modified sim's face.