Late to the party, but that's gonna be for other people if the stumble upon that thread:
Sadly, the whole body material cannot export the UV Template. Two possibilities:
- In your VAM folder, go in \Custom\Atom\Person\Textures\FemaleBase, you will find all the textures for the UV of any female character in the game. Use those as a reference then create your tattoo
- Grab you character, go in the "Control & Physics 1" tab, export the obj (big button at the bottom). Import in any of your prefered 3D software (like Substance painter) and paint your model, just like @Origin69 suggested.