The .pack format is the developers down, which means we can't extract jack **** before they release some tools for it. IE, never.
There is, and has always been, a large modding community for Total War. There are mod tools made for every release and Medieval 2 will be no different. It's largely based on the Rome engine anyway, so existing tools should only need a little revising to work. There was a tool for extracting Rome's pack files, but the format has been changed in Medieval 2 and is not compatible. However, seeing as extracting these files is necessary for any decent mod, I expect we'll see a new pack extractor in the near future.
The .pack format is the developers down, which means we can't extract jack **** before they release some tools for it. IE, never.
CA has announced that in the next update, in a couple weeks, mod tools will be released. More than was released for any other TW, mind you.