Anyone else interested in this? It has the ASMedia ASM2364 controller. Not available yet but it sure seems like a good use for the 1TB NVMe SSD I'm not using. I have a 20 Gbps PCI-e card. I believe ASUS was also working on an enclosure like this but don't think it ever came to market.
https://www.silverstonetek.com/product.php?pid=979&area=en
https://www.silverstonetek.com/product.php?pid=979&area=en