Would it be possible to get a texture update for the virtual mirror to make it look a little less virtual and a little more...well, like a mirror?
You could create an overlay on simhub and sit it over the current virtual mirror if its just the look you want.
In the old Rfactor days, the mirror was just a texture that you could resize to change the resolution and replace. The white box must be a texture of some sort I would of thought, even if the white border was black, it would look better?