Network Lists: Why only Port or IP/Subnet?

Settings > Profiles > Network Lists

Allows you to create groups/lists of objects to be used in other rules in the system. The frustrating limitation is that it only allows you to specify Ports or IPs/Subnets. Why not MAC? Why can't I just choose from a list of Clients to make a list, so if the Client IPs change I don't have to remember to go in and update the list manually?

Example: A list of IPs that I want to treat in a special way compared to other clients on their network via a firewall policy that uses the list. Is there some better way of accomplishing this? I don't want to create yet another VLAN/SSID for just a few clients.