Being able to modify what is returned in View() when?

Effectively just being able to explicitly remove certain objects from what the client sees, and what shows up in the right-click menu. At the moment the only way to pull this off is to give mobs x-ray vision and then update client screen/image overlays every tick to hide stuff they shouldn't be able to see, which still doesnt deal with rclick menu.

Ideally, it should be possible to do stuff like modifying a clients view to only show certain tiles on the screen, such as tiles of the same y value, or north of them, when facing north, while hiding objects behind them completely. Or being able to allow a mob to see x-ray vision in a straight line in front of them, but see normally for everything else.