Displaying the enemy's view range through an overlay, just as we have now for move ranges, would be a nice Goldmember feature to have.
Of course, just like the enemy move range overlay, it should only display publicly known information. However, most of them are fixed anyway (i.e. if a MoneySite is known to belong to the enemy it's view range can be displayed, otherwise not).
A difference to the move range overlay would be that the entire view range overlay is enabled/disabled at once, e.g. through a click or right-click on that player's shield, as opposed to clicking on each individual stack, as done for the move range overlay.
Again, this just saves me from wasting my turn time on counting squares from known enemy units, nothing else.