You might be surprised at how little of the body still functions without brain function, well, some bits of the brain, including basic homeostasis and immune system function.
Yeah, sure. There are probably going to be only a few tens of thousands "unknown unknowns" side-effects but hey, who cares? We will figure them out, we are out of the stone age cave now!
If you toss out the old rule book and provide unlimited funding, it can be made to work.