Sounds like how my network grew, with more cnc'd machines added. But I was never able the make MFSv4 Just Work for anything for more than the next reboot of one of the machines. Then I discovered sshfs which Just Does anything the user can do, it does not allow root access, but since I am the same user number on all machines, I just put whatever needs root in a users tmp dir then ssh login to that machine, become root and then put the file wherever it needs to go. I can do whatever needs done, to any of my machines, currently 7, from a comfy office chair. Stay well all. Cheers, Gene Heskett.
I second the sshfs approach. I use it between several Debian servers and have been happy with the results. Once setup in the fstab a click in a GUI or mount command on the cli mounts the remote server on a directory specified in the fstab.
A sample of a line in the fstab (check docs for more options):
sshfs#root@172.16.0.xxx:/ /mnt/deb-test fuse
user,noauto,rw 0 0
The user at the remote system is root in this example. Not a good idea unless you are the only one who can login to your system. I use ssh keys always. If they are created without a password sshfs won't ask for one when it is mounted (I need this for my backup system Backuppc). I even use sshfs to access a Digital Ocean droplet I have over the internet.
The current NAS you have
might work with sshfs if their ssh server supports SFTP.