Adding an RSS feed via GPO is pretty simple, e.g. import the Administrative Template for Outlook and you get some options to create default RSS feeds.
But there is no way by default to remove certain feeds remotely. You can only e.g. disable the whole RSS feature, but this does not make sense in all cases.
As there is a COM object available to manage feeds, I created a small tool. It lets you delete certain feeds via command-line, and you can also run this file with your group policy object.
All you have to do is to add the existing feed path as parameter.
It returns 0 if the deletion is successful, -1 if the feed does not exist, -2 if there is no parameter.