Seriously...
WHY?
I just can´t get what you would need that for. As if the current one plus basicly any shape using physx would not be enough. Most other engines (for example Unity and ShiVa) do only have the ones supported by the physics engine and no one really complains.
There are much more important things for Gamestudio than collision shapes, so better learn coding, to do at least some things on your own. I btw really doubt that an AABB box would instantly solve all your problems and that the old system is gone without good reason...