There is an option in the Register view to add registers to the Expressions view using the "Watch" option in the context menu. This option is available even for defined bitfields in the Register view. However, when the the bitfield is added to the Expressions view, it only shows a list of registers (which can then be expanded to the bitfield level).  

Basically to what level of granularity is supposed to be supported in the Expressions view? If bitfield level is not intended to be supported, then it should not be added to the Expressions view.