ugh. I'm having such a hard time making myself believe that this is a good idea.
The inevitable result of this is that I'm going to have _two_ copies of most of my system libraries in core at all times, and we'll be back to the bad old days where common software isn't 64 bit clean (right now its mostly only proprietary crap-ware like flash thats problematic)
And for what? so a very few overly pointered memory bandwidth bound test cases can run faster? Any many of these cases could run just as well by switching to (e.g.) using pointer offsets internally (which would also reduce their scalability, but no worse than switching to 32 bit mode).