3sr+buyer,
That is a good idea about having the right turn signal video show on the top right of the display. I think the left turn signal video should be on the top left, unless it's illegal to cover the speedometer for a few seconds. But Tesla move the speedometer to the center of the display when the left signal video comes up.
Yes, cameras as side mirrors would be best thing. Unfortunately, it's illegal for side mirrors to be a camera only so it would have to be a combo thing in what looks like you showed in that picture. Regulators need to catch up with the technology, although many center mirrors are displays for a rear camera.
But ultimately Tesla took the cheap way out and we could have had a more advanced turn signal system. They didn't even give us 1080p cameras when they had to know the cameras would be used as a dashcam/Sentry thing.