There will be some aftermarket PCI-E adapter cards that will fit the 2.5 form factor right in it. PCPer showed one: http://www.pcper.com/reviews/Storage/Intel-SSD-750-Series-12TB-PCIe-and-25-SFF-Review-NVMe-Consumer
http://www.pcper.com/image/view/55023?return=node%2F62712