Your optimism is admirable, but without the cerebral cortex, this kind of rehabilitation is impossible. It's like expecting an amputated leg to grow back.
Your naivete is not.
Since when did what we currently know in medical science become the last advance of its kind? You may think that doctors now know all there is to know about the inner workings of the human brain (and the rest of the body I might add), but I not only could strongly disagree with you, I can point you in the direction of new advances being made as we speak. There are a few doctors who have been kind enough towards brain-damaged people to do further studies with the latest of technology, like PET scans and MRIs, and some doctors are discovering that although some of the cortex looks irreparably damaged that some of the neural fibers are actually looped quite deeply (like the way a carpet is) and it's only the ones on the surface that have been damaged. The others are still functioning although they may be more fragmented. These doctors that I speak of have found that they can coax people out of their so-called vegetative states. The problem is, they've been overlooked, and for a long time we haven't known what "signs" of awareness to look for. My guess is that the Schindlers have cared for their daughter so frequently that they are aware of small changes she makes, when a doctor who visits once in awhile sees nothing. Optimism is appropriate.