CFast is based on the Serial ATA bus, using a female 7-pin SATA data connector, and a female 17-pin power connector. If an adapter is used, can a regular SSD be used in place of a (currently very expensive) CFast card?
Of course there could be problems like the memory card door not closing, the camera can't provide enough power etc, but consider all of those problems solved.
Update: I've found a Kickstarter project called C-Box that is intended for video recording in 4K, but i can't imagine that it won't work for still cameras. Unfortunately I'm not sure whether it contains a bridge or not. Considering the price ($499.95) it would be an astonishingly bad deal if there were no bridge interface in it.