Good points, Asguard.
Here's the deal about brain transplants and/or body transplants: The technology that will allow for such procedures will also be the same technology that allows for cloned bodies, body parts, artificial limbs, cybernetic enhancements as well as nano and nenetic technologies.
So, while we might envision a "brain" transplant, in order to carry one out, you'd need a perfect match or a cloned body. In order to "insert" the brain, you'd need nano-technology to repair and re-attach all the damaged nerve cells.
The technology that will allow for such things will, as a byproduct, negate the necessity for such a procedure.
When that day arrives, our genes will be so enhanced with new information: Imagine knowing EXACTLY what every strand of DNA and accompanying mechanisms did in your cells. Now imagine a human being with a body "built" with 100 pairs of chromosomes instead of a measly 23. Imagine all the extra abilities. Imagine all those "enhanced" abilities augmented even FURTHER with cybernetic technology and nano technology.
The cybernetics can literally be "grown" into you on a sub-cellular level. This may seem crazy, but it's precisely the direction we're going. And it's the ONLY way such a transplant would be possible (through these technologies), and--as I said--any such technology totally removes the need. You can simply conduct repairs on a sub-cellular level and then enhance the body in any way imaginable within the laws of physics.
~String