Rockwell has never been particularly interested in having PanelViews communicate with non-AB PLCs. I believe that the only non-AB protocols supported on PanelViews are Modbus and DeviceNet. If I'm mistaken, I'm sure someone will correct me.
So, if you can get a Modbus or DeviceNet interface for your Mitsubishi, then you can probably use the PanelView. Otherwise, there are several brands of HMI that can communicate with a broad range of PLCs, including Quick Panel, PanelMate, Maple Systems, and many many others.