If I had my own salon my dog would be there. He doesn't jump on people, hardly moults, doesn't lick himself in inappropriate places and prefers to just sit or lie on his bed or on a chair.
He's amazing with kids, will let them do what they want even pull his ears, and when he's had enough he will go in another room and the kids are told to not follow him. He's never snapped, growled or barked at a child, and I have in the past, and will in the future leave children alone with him, I've complete trust that he would never harm them (and I've left him with baby's in carriers, all he wants to do with baby's is lie next to them or put his head on their legs).
I'd not need to check if he needs the loo, he always lets me know when he needs to go, can hold it for a bit and we have only ever had accidents of him pooping in the house when he's been ill.
Clients would be told there would be a dog, so if its allergies they don't have to come, and as for fear, the same again, he doesn't approach people so there's no reason for it. I don't lock him out of any room or in a room at home when we have visitors because its his house too, and I've always had the mid frame of "its his house not yours, don't like it then don't come in".
I think there is a market for everyone, some don't like the idea, and that's fine because there are salons without dogs in them too, but (and until I get my own salon and have my dog there) I have thought there may be a boost in business from having a friendly, calm and clean dog in the shop which people can make a fuss of....
Little fact, stroking a dog can extend your life as the stroking action is relaxing to yourself and the dog creating a bond, releasing endorphins and ultimately prolonging your life unless some unforeseen accident such as a crash should be the reason for death. Xoxo