Just a suggestion, but if you really don't like getting updates from the DGC, why don't you just instruct your users to edit their launcher configs, and put in a dummy patch URL. That way, even if we release an update, your players and their launchers won't grab the latest data, leaving you on the previous (working) version.
Of course you're probably going to need to give them a manual patch bundle, since any new players wouldn't be autopatched to your version.
Unless you figure out how to get the patching system working to your own website, with the required bits of data. It's not really hard to do. It's not locked into our system.
