i do something similar.
i use veeam backup software, community edition, to backup virtual servers and computers.
then i use rclone to copy those backups to the cloud using --backup-dir.
for backups of files, including veeam backup files, i have a python script that runs fastcopy, 7zip and use rclone to copy files to the cloud.
as per my rclone wiki, i enable VSS
as for the central server idea, on my backup server, i run the python script in a timed loop.
there is a shared folder that it looks at.
if a local computer, using that same pythong script, wants something done, it will copy a file to that shared folder.
if the python script finds a file in that shared folder, it looks up that filename in a .ini file and runs a script. this is a better solution then rclone serve, as i can run any script.