I had a somewhat similar setup and it worked pretty good as long as I needed it. A Raspi, which would also do other stuff, like provide the DNS service, would wake up a backup server, which was a Xeon machine and consumed a lot of power, also was running Windows. The Raspi would wake it up 4 times a day, the server had a Task set up to run some Python scripts which invoked robocopy so that the server pulled the data off of another machine which was always on and required to be backed up. When ready it shut itself down and all was good.