I didn't specifically mention whether the unit would overclock or not when docked as I was just talking about getting more power with a dual-dock system. What I would like to see is a system that clocks up when docked, but ALSO having a dual dock system. So based on what people have said so far, we might get a 500GFlops handheld and then start getting up to 800-1TFflop when docked (Probably with active cooling). Add in the ability to dock another device and you start to hit some good floppages when all's said and done. Obviously it's not the same as one device doing it all, but could be a way to allow the power hungry gamer to get what they want, while enabling the units to act alone for families - assuming price is managed of course.
The dock itself, if not augmented may be pretty cheap to make. Power, HDMI, couple of external USB with 2 USB-C/Thunderbolt ports for docking up to 2 units. There's work to be done on the API of course to present this to developers, and the bandwidth won't be as high as RAM but it would certainly start looking mighty attractive.
I'm not sure how much removing screen and controls would save but they could even do a "dumb" unit that you dock along with the real one, which is effectively just control logic, RAM and GPU, although that would add another SKU which may confuse things.
If I was looking at getting an NX, something like I proposed would be VERY attractive and I would personally pay US$399 for that setup. I could game with XBO/PS4 level graphics, and then me, my wife or children could have their own personal game machines for living room/bed play etc.