From the developer forum:
> Is there any chance that the mesh formats and
> could be extended to handle other vectors of the
> space (not just normals, but tangents and binormals too)?
> These vectors are commonly needed for per-pixel
> and cannot be simulated with extra texture coordinates
> (since they must be properly skinned).
This is something to look into. Are there any other
kinds of data that might be useful? What are the
equations for finding such things?