The problem with "kinking" the system is that you downplay the "service" part of true service animals. We are lucky that we have small dogs that can go many places with us. I take Sammy and Loki (usually one at a time) places that I could NEVER take a large dog, simply because I can hold them in my arms or they can ride in a carrier. But I don't take them anywhere they are not allowed, like restaurants or the grocery store. If it's a clothing store or something I don't ASK first, but if I am asked to leave I will. I was only asked to leave once because I set Loki down on the floor (in a sit-stay) while I re-adjusted my purse and zipped my coat. Again proving my theory about little dogs... Also, I have found stores that love them so much they insist that I let them walk and play with them while I shop, so I go to those places more often!!
There is a LOT of training involved and your dog would have to wear the vest/harness whenever he is with you. It's not like you carry your dog shopping with you and when someone kicks you out you pull out the paperwork. That just frustrates business owners because then other people are going to want to bring their dogs in too. No one would look at a golden retriever with a seeing eye dog harness on and say "that's not fair!" because the dog was in a store. At a restaurant, service dogs lie at your feet under the table and are supposed to be silent and as close to invisible as possible. No one is allowed to pet them. They are "working." So please consider that.
I'm not trying to lecture - I've spent 2 years in the *very* amateur dog training world so I've learned a bit about it. I'm not quite sure most Yorkies are exactly meant to be service dogs. Loki is smarter than 75% of the dogs we were in classes with. He learns the tricks/commands/routines faster than any other dog. But that doesn't mean he was the best dog - far from it. He was simply too distracted - too many smells and sounds and whatever. Obviously you know your dog and this may not apply. No matter what there is a LOT of training involved. Plus, as was stated above, you do have to train him to perform a function. I mean, Loki could fetch all the socks that I drop out of the laundry basket on my way upstairs if I asked him to - but I don't *need* him to do that
Maybe you just need to seek out more places to take your pup? We find that outdoor style malls are the most friendly. I'd say I take at least one of these guys with me about half the time I go out.
If you are really interested, sign up for Canine Good Citizen and move on to TDI (Therapy Dog International?) If your dog can pass those tests then you have a shot, plus you will already be involved with the training community if you choose to go further.