This unit is compliant. There is no improvement to be made in that sense.
systemd simply does not support defining a custom action for
systemctl status foo, unlike the
init.d scripts in System V init.
systemd can only check for a running daemon (or not, given
systemd does not track units for network status, IP addresses, nor the legacy interface aliases you're using.
You could change your main network configuration system instead, to include the second IP address. You might enjoy having all your network address configuration in the same place :).
systemd-networkd supports running DHCP and static addresses on the same interface. NetworkManager does not, but nowadays you can create a keyfile to create virtual macvlan interfaces as children of the physical one. (In theory this might even allow you to request multiple DHCP addresses :). Do not try to apply configurations from more than one of these configuration systems to the same named interface. If you're already running NetworkManager, it's probably easiest to use that.
Both systemd-network (networkctl) and NetworkManager (e.g. nmcli) will then detect and show if you change their network interfaces yourself.
It may also be possible to configure older config systems to create macvlan interfaces. However, from what I remember, they could get quite confused if you mess around with the interfaces behind their backs.
Additional custom pre-up or post-up tasks could be hacked up in most configuration systems if necessary, although systemd-networkd does not have any such system built-in. I say "hacked", because the NM system isn't really designed to run scripts written for one specific interface.