You wouldn't want FMS to back up to the network for precisely this reason: fragile and slow. For its normal backups FMS can take advantage of hard links which makes it very fast and very efficient with the hard disk space.
Hard Links are normally not preserved when copying to an external drive or a network drive which is why it is so much slower and uses a lot of disk space on the receiving end.
Look into using a copy tool that uses Rsync 3.7 (which is more modern than what ships with OSX - cc uses the OSX version of rsync). There are ways to preserve hard links, certainly to external drives, not sure to networked drives.
One option is to zip the backup before pushing it to the network. But that is going to be processor intensive on the FMS box.