Well this could be easily be done in a humane way, and I bet it is. I'd do it by personally taking care of the dogs myself and letting each dog have at least a couple of weeks off between "visits". Charge these fashion conscious people a premium and gives the dogs a luxurious existence with a dedicated owner and caretaker, and take care of them when they're too old to do this stuff any more, and I'd say you're being humane.
It's true a dog is smart enough to have a personality and to feel pain and empathy, and yes I like dogs better than many people, but it's still a dog. It doesn't have aspirations or values or desires, just needs. A dog isn't going to be upset that it is not free to pursue its dream of being an attorney.
Really have none of you left your dog or other animal with someone else for a week or two, or had someone ask to borrow your cat? Dogs have been earning their keep as hunting companions, guides, trackers, and eyes for the blind for quite some time now and no one considers those dogs to be mistreated. They can be escorts too.
If nothing else it's a far kinder fate than being kept for a short time by a shallow and fickle owner and then discarded, perhaps in a dumpster.