The left and right side mirrors would rotate inward to reduce the chance of scraping in tight places and make it easier for people to walk by a parked car with folded mirrors.
Controls should offer auto and manual modes. In Auto, the mirrors auto-fold in when the security system is active and open when walking up to the vehicle or perhaps when sitting down. In manual mode, the mirrors can be set to fold in or out.
A bonus would be to have the mirrors fold in when parking at home (although the logic for this could be tricky to avoid having them close when leaving). For example, fold-in might occur when the GPS identifies the home location AND the car is not in reverse AND HomeLink is pressed to open the Garage door.
Many luxury vehicles provide this either as a standard feature or within a larger tech package. We priced out replacement electric folding side mirrors for a 2010 Ford Expedition with memory at $530 for both mirrors from CarID as one source.
I absolutely need this. I even asked Elon Musk at the Munich Service Centre reception and he said that it would come as a retrofit.
My garage is so narrow that I have to fold them in manually every time I enter. The neighbors are laughing: Here comes the most modern car - all electric and all with big software driven things, big screen ... and no matter what the weather is like I have to open the windows, lean over and manually pull the mirrors in...
Power-folding mirrors, or no mirrors at all, are pretty much a requirement in Europe's narrower streets and parking places. A car of this size and price will be hard to sell in Europe with large, manually folding mirrors!
Regarding the suggestion to replace mirrors with cameras, I guess you really have to try it. Although I haven't tried it myself and would be very curious to do so, the difference between the two systems may be substantially larger than most expect: In a mirror, you have an actual parallax and thus 3D vision. That's completely lacking in a (single-lens) camera image. This difference may be subtle but irritating or annoying.
I doubt the weight is an issue. The tiny motors for two mirrors and related stuff can't be over a pound or two. They trimmed the mirrors with metal. My guess if they used plastic the net difference would be zero.
Power folding mirrors does add a little complexity (wiring, controls, software) and added cost to the overall design. I expect either meeting the desired cost point and/or eliminating some items to meet the production deadlines was more likely the choice they made.
The Model X's elimination of the mirrors entirely seems like a better way to go.
This was one of the reasons I hesitated on getting my S. This car is WIDE, wider than my wife's Lexus GX SUV. Between my narrow 1930's garage (I have had it widened so I now have 5" spare room with both side mirrors extended) and parking spaces, it is going to get dinged. I would love to try to reduce some of those by having the side mirrors automatically fold with the push of a button (or programmed to close when the key is out of range).
My old 3 series BMW has had this feature for almost 10 years I think. Seems like a basic for a car this price.
Down the road, I would gladly pay to get some aftermarket ones (from MB) put on, if they can integrate with the computer system.