I don't know who maintains the ports/packages in FreeBSD 9+, but How about a separate package for each SQL front end like under debian?

[root@server:~]apt-cache search zabbix
zabbix-server-mysql - network monitoring solution - server (using MySQL)
zabbix-server-pgsql - network monitoring solution - server (using PostgreSQL)
...
zabbix-proxy-mysql - network monitoring solution - proxy (using MySQL)
zabbix-proxy-pgsql - network monitoring solution - proxy (using PostgreSQL)
zabbix-proxy-sqlite3 - network monitoring solution - proxy (using SQLite3)

But on FreeBSD
[root@beastie:~]pkg search zabbix24
zabbix24-agent-2.4.3
zabbix24-frontend-2.4.3
zabbix24-proxy-2.4.3
zabbix24-server-2.4.3

And as for me, who doesn't like MySQL, I had to compile manually from ports an lock the packed, because otherwise is always get "updated" (Options changed)
Especially for the a small Proxy the sqlite Option is much more interesting than a postgres or a MySQL, and can make updates much easier.