EOC has been designed for such scenario, it would be the best option for the central site.
If you do not have EOC, Users in the central sites will have to connect to the 16 different web consoles to monitor all the nodes instead of connecting to 1 web console.
All the other way would lead, I suppose, to try to reproduce the behavior of EOC with internally created tools.
Note that EOC does not cover the NCM module, only the APM, NTA and VoIP modules and of course Orion NPM. So you will still have to connect to the 16 NCM web sites to review configs/policy reports results.
I'm going to demo it this week.
What's the best way to contact a sales engineer with my queries prior to purchasing?