Just as an addition here:
Has anyone considered the OS native "linux subsystem for windows"?
It should be possible to add the proxmox sources to that and then install the client within the subsystem. Then use a planned task to start the bash with a backup script.
*EDIT: I just tried and it's possible to install it within the subsystem for linux. Backups also run flawlessly. I also opened some Word documents within that folder and all files were still readable. But maybe there's also another case where "opened files" fail, I don't know enough about word to know if it really keeps the file handle open.
