I would think if you got a GSD as a puppy and raised it with your Yorkie things should be OK. Our other pets are cats, my GSD was raised with them and she loves them (although not all love her!). In general, my adult female GSD tends to be drawn to the small, male dogs. She is so gentle and kind to them and always wants to meet them.
How does your Yorkie react to other dogs? Is he generally friendly and wanting to play?