No, I don't. At least on paper sure you could do it but, in this world, a world I like to call Reality, I don't think it's possible.
There are some fish that will not make it through a medicated or hyposalinity QT. Commonly some wrasses and mandarins for example.
You'd have to have a separate Coral QT from your fish QT and you would need to keep your coral in there for the period that it takes ich to die. This means you could only add coral once every 6-8 weeks...I don't know ANY reefer than can withstand that. The minute you add another coral, 6-8 week clock starts over.
So technically, assuming you have the time and resource to do it this way, sure it's possible. But I have yet to meet a reefer that does this. Most QT fish and forget that water and cysts go into their tank with other livestock like coral and clams, etc. Although it's improbable that ich would be introduced this way, it's not impossible. I would expect that professional aquariums would have the staff and resources but most of us couldn't/wouldn't.