Well, basically the WX 5100 is a Baffin-based workstation card (RX 460 is also Baffin), with a TDP of about 75W and a single slot wide (which is a plus). Whether this card actually has any other advantages over the vanilla RX 460 (other than the huge 8 GB VRAM and being single-slot) is unclear. The price is a clear downside though (roughly 3 times the price of a 460).
I'm assuming the WX's drivers come in the same package as the 460's drivers. That would also indicate that the WX4100/7100 might also work.
Price of course still a big downside with this performance. But 4x 8GB VRAM single slot cards with internal power only (up to ~16 TFLOPS in total) is now possible on the cMP. Which is surely a good sign. An expensive upgrade still better than no way to upgrade, right?