I think there are many reasons why the glass rear roof wont change, whether that be, the need to allow height for rear passengers, too much redesign, the fact that some of us like it, the fact that competitive ICE sedans have the same trunk, the cage would need reworking, as well including safety tests, it's just too much too late on. Nevertheless here is a solution to some of those problems taken from the Honda Fit, a small hatchback. Obviously it doesn't solve the problem of carrying cargo including 5 people, but as the space at the back isn't that large, a liftback with 5 people in and no flat 2nd row seat wont offer much more cargo space anyway, unless the rear height is massively increased to resemble a hatchback. Solution: The front passenger seat folds down allowing 2-3 people to ride in car with as well as long object. I have done this with 2x4's, I think I got over 30 stacked up in it could have doubled it. The 2nd row folds up allowing tall and wide objects. I have fitted large square shower trays on their side and a bike standing in it which I couldn't do in 99% of trunks of any car. BTW the 2nd row seats are split in 2 so 1 can remain as a seat whilst the other 2 are lifted or vice versa.