There are good reasons why mainstream auto makers stick with traditional swinging or sliding doors for their designs.
Upward opening doors are:
- Harder to seal reliably (more gasket area, different closing forces)
- Harder for passengers to open and close manually
- Slow to open and close if they are electric, or in an emergency
- If the vehicle rolls over, the doors are difficult to open
- More work in terms of crash engineering
And, this design would preven a customer from mounting a roof rack for skis or bicycles.
Tesla could have simply designed a nice set of sliding doors, but it is clear they want to be different. I think the electric powertrain and Silicon Valley pedigree of the vehicle makes it different enough.
They also have a significant risk in terms of market demand for this type of vehicle--neither the BMW X6 nor the Honda Crosstour are selling very well.