I know there are IP address groups that could possibly be used for this but I think using them for other things plus this would be confusing. So I think this being a resource on its own would be helpful.
If we could name our sites by address groups or ranges I think that would put a whole new spin on NTA. Being able to see the top sites for traffic in general or more specifically a certain type of traffic would be helpful.
So maybe you could see things like what sites were pulling the most exchange data or create alerts on a site that BAD traffic types go over 1% usage or maybe a site that VOIP goes over 50% utilization of the link.
Obviously sites would just about directly correlate to the router that is the source of the data but this would be more granular however maybe this would be a way to create them by say creating a "site" and linking it to a NTA source.