So doing a deep look I see Munin is based on database/rrdtool too. Icinga and LibreNMS as well.
What about running monitoring tools from a FreeBSD Linode VM. That is where I think I want to go. Cloud based management.
I think it's good idea to separate zabbix in a VM. As most of our FreeBSD servers are in Hetzner datacenter we use a Hetzner Cloud VPS running Debian (they don't support FreeBSD in their cloud) for Zabbix (I use snmp with custom scripts and not zabbix agents). We also use external monitoring from NodePing.com (they have good prices and so far are very reliable). Finally we use Monit to restart services in case they crash and run some custom scripts for disk cleanups if the disk usage is more than 80%.