I have a Sony A7s and I know it is not possible to connect to it, unless you are using the Sony software, which I use successfully for my intervalometer aspect of the images.
Will it be possible, to have the auto focus control function open the RAWs that I get when the intervalometer is working and look at the latest image (or even the previous ones if needed) and then estimate the change in focus by looking at the stars, then correct the focus, and wait for the next image? The process could be slow, but it could help maintain the focus through the night.
Thanks
Alvaro