IIRC there is no open/free source decoder for bluray due to the content restrictions on them hence one can not integrated into MP. DVD's only work because MS supplies a decoder with the OS and there are open/free source ones available.
So for the moment you're stuck, like me, having to use the PDVD plugin to watch blurays
I am fairly sure the main problem is the menus.IIRC there is no open/free source decoder for bluray due to the content restrictions on them hence one can not integrated into MP. DVD's only work because MS supplies a decoder with the OS and there are open/free source ones available.
So for the moment you're stuck, like me, having to use the PDVD plugin to watch blurays