I know I'm late to the party here but what about retired military working dogs? The husband and I had planned to go that direction but we had a 12 lb little alpha boy to worry about so we went with a puppy. Our next GSD will be a retired MWD though and many of them are ready for a slower pace so do not need all the exercise of younger dogs of any breed and they are very well trained well before you get them.
Maybe I misread, I didn't read all the posts. If they can't handle a GSD and asked about another breed, why could they handle a retired military dog.
My friend trains Malinois for the military. You think a family could handle a military dog if they can't handle a pet GSD? They are crazy animals.