Sony’s concept of an A-mount mirrorless was similar to the K-01 from Pentax (but with a different design).
As I told you before Sony changed the camera roadmap. And from the three FF camera prototypes that I heard off two were taken off the roadmap. One is the A1X FF SLT and the second is the A-mount Full Frame mirrorless camera (without SLT mirror). That was the most compact A-mount camera ever made (in Sony lab). It would have become a sort of entry-level and cheap Full Frame camera. I now have been told by two sources that Sony dropped the idea to release a camera like that. You may let me know if you would ever have considered to buy a camera like that
By the way, Sony wouldn’t have been the first to use the same classic DSLR mount for a mirrorless camera. Pentax did it with the futuristic (or horrible) designed K-01 (available in different colors on eBay).