This post from Jeremy Moskowitz is great to centralize GPO’s.
Here’s a piece of the article.
You’ve probably heard of the Group Policy Central Store, but didn’t know what it does, or where to start.
Kind of like Dorothy’s ruby slippers, it was right under your nose, the whole time, waiting for you to use it. So, before we get into that, let’s explore first what the Central Store tries to solve and where it was born from.
Microsoft had a format to describe “what’s possible” in Group Policy using a formatted, simple language called ADM files. ADM files were great because they were simple, quite readable plain text files. They described the policy setting, what the general parameters when edited, and what registry setting to control.
Microsoft shipped a handful of these in the box with Windows XP, and added more with utilities like Office and some others.
Group Policy Template and ADM Files
Let’s explore the “physics” of what would happen with Windows XP and ADM files. Let’s assume you created a new GPO from scratch:
You’d fire up the GPMC on Windows XP.”
Read more here.