I'm legally blind and want to train my dog to be my guide and I need some direction with equipment. Do you feel that Aussies can make good protection dogs?

I have an Aussie I'm looking into training for assistance work. I'm legally blind and so am hoping to get her going as a basic guide, but I also want her to carry a backpack for me. Because of that, a harness wouldn't be practical for use in leading me, so someone suggested using an agitation collar. That way, her back would be free for the pack but I could still have a handle to grip that was close to the dog and very different than a training collar.

Could you give me some kind of price estimate on how much this would be to make? She's small, about 19 inches at the shoulder and probably takes an 18-inch flat collar. Another question I had for you was how you thought she might serve as a protection dog if necessary. Because I'm blind as well as a single female, it's important to me to have a dog that I could rely on if the need arose. I'm not talking about formal training here, but generally speaking, what is your opinion on Aussies as personal protection dogs? If someone jumped on me out of a dark alley, would the typical Aussie be a dog who would stand up for me?

I really appreciate your help, and look forward to hearing from you!

Anne