Yah, I just don't think the SMB subsystem is robust enough to be used for that purpose. I can see pulling a few files on and off, but expecting the PHP backend to work with it to manage file locks etc on SMB is probably optimistic. Plus because docker is involved, I believe overlayfs would be involved there, unless it's a bind mount. Then you have a layer between OMV managing the communication between it's underlying filesystem to the samba server it implements. I'm really not 100% sure what the pipeline to the actual files would look like. But it seems horrendous.
I'd really just try it stock before you throw that baby out, because I've run NC every way you can possibly imagine since about V.8, and I've not had so little problems with it as with using the AIO. It's head and shoulders above straight installation, somewhat better than NC-Pi. Snap was by far the worst for management and upgrade. And I would avoid Ubuntu as the host system, because I have no idea how docker snap got installed, but I don't trust that it wouldn't happen again. I sure as hell didn't install the snap version, but there it was.
Also, with the AIO, I would avoid managing anything outside the interface of the master container, like by using portainer on the child containers.