Not only would it be nice for the camera manufacturers to give the user the option to enable a true raw histogram, but it would also be nice if there was a simple firmware addition that would enable the user to be able to input a raw offset, in EV, that would simultaneously permit exposing/shooting ETTR for raw and then simply scaling the ETTR downward by the user inputted EV offset for the in-camera JPEG. If you shoot raw+JPEG but ETTR, currently the JPEG is rarely useful because of the added exposure for the ETTR.
Cameras like Fujifilm let the user process the raw file in-camera after the acquisition to generate a new JPEG - in-camera raw conversion. One of the controls is exposure compensation after-the-fact. So, it is already available but is an extra step that the user has to deliberately perform manually.
In other words, if your cameras shoot raw, then give raw shooters the tools to take advantage of it.
kirk