Stuart,
I am pretty sure you can use the object from ExtendScript. With the FDK documentation you should be able to guess the property names in ExtendScript, but the easiest way is to use a small test document and write a small script to get at the GraphicsFmt object. Set a breakpoint and use the Data Browser and/or JavaScript Console to see how FM uses the object.
As for better ExtendScript documentation: I am working on a website (www.progframe.com) that will feature better documentation, combining the current docs with stuff picked up from the FDK reference and test scripts. It will also have tutorials for newbie scripters. If Adobe does not put an effort into the docs, I might as well do it and possibly pick up some scripting jobs that way. I am planning to launch the website early next year and keeping it up to date so that ExtendScript info is immediately available when a new FM version hits the market.
Kind regards
Jang