I know a lot of people angry about V9 removed the functionality of stick top rear view camera. There're petitions, rants allover the internet.
TL,DR: you won't get it, and Tesla won't change it, the reason is because UI interaction logic is totally changed in v9 to satisfy the future product.
Current design of vertical screen on S/X is the 1st generation from 2009, the interaction of two screen split with top and bottom works perfectly for present and past. But if Tesla wan't to move further, provide more features and streamline experience, they have to think about the future.
1. v9 UI change is based on the great feedback of Model 3's UI. It wins lots of reviewers' heart and give Tesla a confidence to implement it across all product to streamline the UI interactions. Tesla's mentality is: If new user can live without a permeant rear view camera, so can you.
2. According to the leaked rendering from new Model S/X Dashboard, it will use the same horizontal screen like Model 3 and Semi, instead of current vertical screen:
Semi
Refreshed S/X (assumed change)
3. Most importantly, Tesla want's to emphasis the importance of Map for the advent of autonomous driving. After you achieve high level of Semi/full autonomous driving, what would be the next big thing? Not surprise:
entertainment. That's why the media/stream player got their next best attention on v9, you can have all kinds of customization on media player, new features, but not with other apps like the rear view camera we talk here.
4. Tesla have a track record of never ever bring back old features because of people's voice:
When v7 introduced to fleet, you lose the analog speedometer on Autopilot equipped cars. Lots of people hate it, but they never provide a button to switch the speedometer.
When UI moved from v7 to v8, they purposely added auto-hide top menu, lots of people hate it, but Tesla never provide a button to auto-hide/show the top menu.
When v8 brings the new media player, it broke the USB player, after two years of struggle, it still the same.
And like iPhone, you can never downgrade a firmware, whatever Tesla feeds, you eat, they never listen.