If the Alienware back-pack is based around the Alpha it could be a more viable option than some of the other offerings; less upgradeable of course, but I'd rather strap an Alpha to my back as those are tiny. Still requires batteries of course, but they're pretty good on power consumption, unlike more modular systems. Though I'm not sure if the 960 has enough power for VR? Of course every GPU maker is trying to convince us only their latest GPUs are good enough, and I'm not convinced that that is true.
That external graphics brick however is hideous; the full-sized PSU just makes it far too big, it really needs a custom PSU that fit a better form factor. In fact a vertical design could be a lot more interesting with a PSU at the bottom and the card oriented to expel air from the top, it'd be easier to tuck under a desk or behind a monitor or such this way too, a wide, long box just doesn't really mesh well with a compact laptop.