some times we have scenes where a big flat mirror is dominant, maybe used for making a room bigger ... . The mirrored space is important like the space in front.
A little bit I understand the limitations of screens space calculation. But the view through the mirror is the same like done by a camera from behind the mirror if the camera would be placed at the same (but mirrored) location like the original camera. (I hope I found the right words to explain it). So, if the scene isn't heavy, couldn't we not get the calculation of the second mirrored camera too and shown at the mirror? For this need it could be great to get a special keyword like "supermirror" for activating the additional calculation.
Maybe no second camera is needed for this special calculation, anything could be done for a "folded" room, the space behind the mirror act like the "real" space in front. (For example the depth map could be calculated for the mirrored space too or not?)
I think on light scenes like a bath room or a air plane lavatory. Here a photo example from the www.