What can of worms would a dash can open?
They are lady have cameras looking fore and aft, right? Just record the last ~x hours of video to an SSD and offer the ability to offload it to USB and/or view it via app.
I can think of many worms in that can...
+ Tesla can get dragged into court and for lawsuits to validate dash cam videos
+ Tesla may get dragged into court and compelled to produce/disclose videos recorded by the car
+ Some customers may want audio recording and though that is possible with the car's microphone it is illegal in some jurisdictions
+ What if there is a major accident and the dash cam video is corrupted, I'm sure Tesla has better things to do that rebuild dash cam video files
+ Tesla will have to release software to manage the dash cam videos (perhaps those resources are better put to use improving the navigation system).
+ When that dash cam software has issues, wait till you read all the "I paid $100K for a car and it can't even record video" threads...
+ Tesla will have to support whiney users and all their dash cam problems. If you thought not having backup lines on the rear camera was bad...
+ It will basically be a thankless mess of worms for Tesla that will give them nothing but headaches.
They should just make available a 12V power source and let users install the best dash cam that meets their needs.