Could you please make a video of your beanchmarks between the default GPU (GT 755M) vs the R9 Nano (with a mPCIe adapter and your ultrabay adapter), and upload it to YouTube? That will get more Y510p owners impressed, and definitely increase the demand of your adapter.
Also, as somebody already told you: I think that your UltraBay to PCIe 3.0 x16 @ x8 adapter is amazing, but this will add stress to the Y510p motherboard because of the weight of a desktop VGA attached to it, and many people (like me) use cooling pads, so it will be a little complicated to use the laptop as regular... So, what about a cable solution too?
I mean: Your adapter can end in the edge of the laptop (as long/large as the ultrabay compartment), and then we can use a PCIe x16 extender cable, but this solution wouldn't be much flexible like the cable that uses the mPCIe adapters (looks like an HDMI cable).
As far as I know, concerning the physical layer of the PCIe (electrical pinout):
PCIe x16: 164pins (2x82), with 6 pins not connected, and 68 grounds that can be a single wire, right?
PCIe x16 @ x8: 164pins (2x82), with 39 pins not connected, and 68 grounds. This will require 58 wires, right? <- your adapter.
PCIe x8: 98pins (2x49), with 4 pins not connected, and 37 grounds.
Although the wikipedia page doesn't match exactly with the interfacebus.com one (11A, 12B and 82B)... I think that the idea would be the same...
Something important too: the impedance of the cable... and as the signals are differential pairs (2 pairs per lane), I suppose that this would require a cable with at least 17 twisted-pair wires for x16 @ x8, (8 lanes + refclock diff signal) and 24 simple wires...
Anyway, I didn't saw again any electronic design since I graduated from the university (6 years ago), so it's sure that somewhere I'm making a mistake or forgetting something important...
Again, great job man! I'm interested in your adapter.
P.S.: Sorry for my bad english.