A GAN would be helpful more for its latent space abilities than for any text-to-image capability. If you look at the GAN papers, you can see that they demonstrate how you can warp an image across multiple semantic dimensions like adding/remove eyeglasses, darkening hair, turning frowns into smiles etc. This would be great for sketches because you can have the victim walk through the latent space by recognizing which version looks more like the attacker, since people can recognize faces far better than they can verbalize detailed descriptions.
