I've shaved a lot of short haired dogs and cats over my grooming career. For some it's for shedding, others because they have allergies and need to be able to quickly and easily do frequent bathing to keep their allergies under control.
There's really no right or wrong blade for it, as long as the dog's skin can handle it. Some groomers would refuse to do it. Some would only use a particular blade length.
If the dog's skin doesn't become irritated, a short shave isn't a horrible thing. Competitors and show people (and some pet groomers) shave poodle feet with 40 blades. One of my poodles can handle a 30 on his face and feet. One I can't do shorter than a 10.
My preference would be a 5 or 7 against the grain, which would leave it very short. I would use one of those because I think it would be easier to get a smooth shave that way.
If you don't go after what you want, you'll never have it. If you don't ask, the answer is always no. If you don't step forward, you're always in the same place.