"they don't work on the brain dead."My guess is that they won't work on PVS patients either.
This is starting to cross over into the Dr. Frankenstein arena -- actually worse, the monster had a functioning brain.
Precise word usage is critically important. The terms "brain dead" and "PVS" have medical and legal meaning. It's analogous to the difference between the terms "baby" and "fetus". The issues are complex enough without confusing things even more through careless misuse of terminology.
A "brain-dead" person is dead. A person in a PVS is not.