I generally don't like harnesses because they spread the weight out, making it so your dog can pull easier. For smaller breeds harnesses are ok, but larger ones I would try something like a martingale collar, metal buckle, or gentle leader.
As for not using treats what type of training do you reccomend a person use? What type of training do you do if not with treats, or some form of motivation?
The majority of the training community have found that a diverse training method, focues on positive reinforcement works better than the old school push your dogs nose in the pee to make him realize not to go the bathroom in the house.
For dogs with agression, and fear, treats are a good tool to help make these dogs better, in a faster more reliable method. Clickers can be seen as a result of the Pavlov's theories. As someone who is an educator as well for kids I also have to disagree with something else you mentioned, about not rewarding kids for good behavior. I look at it this way, if you went everyday to your job, didn't hear a bit of good progress, never got paid for your work, got a raise, would you keep working for that person??? No, I think not.