My first thought was to see if this could be accomplished by using the Windows API's, but according to this website about the Win32 Printer Forms API, it's not even possible to delete system forms programmatically:
One cannot DeleteForm() on a builtin form: it fails with ERROR_INVALID_PARAMETER.
My second thought was to find a relatively unique form name, such as
US Std Fanfold and search the whole registry. Surprisingly, the entry crops in quite a number of places. My suggestion, therefore, would be to build a blank 32 bit machine (32 bit to avoid confusion with shadow keys) and go to town on some of those keys. If you get it working it should be easy to transpose to wherever you need to do this.
However, it has to be said, that given how much Microsoft clearly don't want you to do this, you are opening yourself up to support and compatibility issues.