Who is the target audience for this again?
For low power and bus powered video card, I would take Skylake Celeron 3955U* laptop with 4GB RAM (single channel), Thunderbolt III, 90W AC adapter, usb-C cable, GT 730 GDDR5 (encased by an inexpensive enclosure, bus powered).
That GT 730 GDDR5 (or a future low power desktop Maxwell/Pascal card) is going to be way faster than Celeron 12EU GT1 (with single channel RAM).
And 3955U CPU (15W Skylake 2C/2T @ 2 Ghz) is no slouch either. It should be around the performance of a stock speed E8400 C2D.
*Assuming I can't get Thunderbolt III with Skylake Pentium 4405U (15W 2.1 Ghz 2C/
4T). See post
#59.
P.S. Even if I had a 15W Core i3 Skylake with GT2 and dual channel RAM, a GT 730 GDDR5 still wins (and probably by a pretty good margin as well.) And over time, the gap between Skylake ULV GT2 dual channel iGPU and low power external dGPU will only increase as Nvidia and AMD release higher performing cards in the same power envelope on 14nm. (Even a 28nm 40W Maxwell card would be faster than the Kepler GT 730 GDDR5).
The 730 is not really a gaming card, it's a video playback card. It's significantly less capable than iris pro 6200, and while I know Iris Pro is pricey, I cannot see how it would be economical to purchase an external enclosure and a 730, and not be able to outperform Iris Pro in a lower TDP.
Iris Pro 6200 is only found with 47W laptop and greater.
That is going to make for a much larger laptop.