As a critical Care RN (now retired) I've seen dozens of sad cases wherein a brain-dead person has been kept on life support for months because some religious fanatic in the family browbeats the others by claiming that pulling the plug is murder. The real sin lies in prolonging life mechanically when there's no quality of life. I haven't been afraid of death since my tour as a Combat Infantryman in Vietnam, but my experiences as a Nurse cause me to dread the process of a prolonged death.

Once brain dead, there is no way to recover.

Seriously though is you were really brain dead then you would not want anything. Brain dead means not having to worry about anything because you are basically dead already.
I think the question should be reversed, so as to ask about future wishes.

How would I know? If it wasn't my time to die, I wouldn't.