Haha, this got me thinking. I need my machine to be portable, but when I'm porting it around I'm also generally carrying 30-50+ pounds of camera/lighting/support gear. So, portable is important, but I'm okay with something that isn't the most portable in it's class.
It would be really nice if Apple would make a niche 'Pro' machine that was a little less portable, had really good heat dissipation, powerful CPU and GPU (with 4GB+ vRAM), user upgradable RAM and storage, Apple build quality that we know and love. I bet they would sell the heck out of them. There is a lot of territory between "18mm thin" and Mac Pro. When pigs fly, I know...