TriMeshBox is implemented now, too. I just convert the Box into a TriMesh in the Collider. There may be some bugs in it though (espacially with not 2x2x2 boxes), because I use some crude trick (I misuse the rotation matrix to also contain scaling) to set the size of the box, so I don't have to set the vertices all the time.
Come on, that's a clever trick and if simple I hadn't thought of it. But why in the world do you need to hack the rotation matrix to contain scaling, and how is it difficult to generate the triangles for a box ??
Ah, you mean a box dimension can change and that's the problem ?