I found functions in the plugin code in quotation marks. Do they call the built-in babylon.js functions? If so, is it possible to assign rotation functions to the b3dmodel object?
When you see something saying "mesh.rotation.x/y/z" that's where rotation is applied.
It's true that beyond the automatic rotation around Z (actually Y axis in Babylon.js) depending on the C2 object angle an imported model can currently not change X/Y(Z) rotation. However these rotation options will be in the next update.