Using /etc/rc.conf.d/* for configuring services works well, but I ran into an issue with DHCP.
Where should you put these lines? :
ifconfig_ix0="SYNCDHCP" background_dhclient="YES"
Network interfaces are configured via /etc/rc.d/netif. At the bottom of of this file, it has:
# Load the old "network" config file also for compatibility. # This is needed for mfsBSD at least. load_rc_config network load_rc_config $name
So the "network" config file is soft-deprecated, and the values of /etc/rc.conf.d/network are loaded for backwards compatibility. The correct place to put your networking config (ifconfig_*) would be /etc/rc.conf.d/netif.
However, /etc/rc.d/dhclient needs to read the ifconfig_* values, but it only reads /etc/rc.conf.d/dhclient and /etc/rc.conf.d/network.
The proposed change would allow you to centralize all of your networking config including dhclient-specific variables in /etc/rc.conf.d/netif which to my understanding is the correct and modern place to do this.