This, and this is why I loved the 17" MBP. I'd love a 19" rMBP with 4K or even native QHD screen, dedicated graphics, two SSDs (M.2 would be fine), lots of fast IO ports, and an all-day battery. I don't care how thin it is. It would spend most of the time docked to 2 or 3 external 4K displays for "real work", but then come with me to meetings and on trips.
The only thing that comes close right now is a Thinkpad P70. Can get it with 64GB ECC RAM, Xeon E3-1505m, 4K 17" screen, 2 SSDs + 1 HDD, and a Quadro M5000M. The only problem is that it can't run OSX in some supported fashion, and the battery life likely isn't great. Sad that Apple has been falling short in the professional market for a while now and they expect everyone to be happy with thinner & lighter.