Do the zfs in proxmox and assign virtual disks to omv as needed. Pi-hole works well as a vm and even as a container. A samba ad will work to I am sure. Search for active directory and choose a version that is shown to work with omv. Before setting it up and beating your head against the wall. I am using windows 2012 server but will dump that when it goes end of life.
Had freenas a long time ago. Dumped it as I am more familiar with debian/linux than freebsd. Your milage may very.
I ifirc Votedev (the developer here) was part of freenas years ago.
So you are suggesting i should run second server on proxmox too? Then OMV as VM?
I already have pihole working in lxc and samba ad ubuntu.
I could do the same on second server...this is for HA...