Good luck with that - for most part, there's only been a couple of people who have successfully 'broken into' the Xbox 360 code to extract much of anything, and they are for most part, aren't talking much about it.
It's because im@s 2 uses a different encryption method, which in turn means your previous extraction tools (based from Live for You most likely, or maybe SP) won't work.
From my knowledge, they were working on backporting some of the items to Live for You. (From memory, moving Ritsuko and a couple of the costumes back)
Your best bet (Although I'd say good luck if you do) is to talk with them about it, and see if they'll give you what you'll need.
There was also a successful attempt of getting the models out of Live for you, but Hibiki isn't part of that group.