Every car needs one of these..

[Steve Krug]

DISAPPEARING CAR DOOR - For those those who are too lazy to open a regular door.

Also the supporting brace that runs from the roll cage down to the lower chassis section is removed, which decreases structural integrity under a side impact crash, unless, the door is made out of a material in which that is so strong it can stand up to that abuse, although then it will be so cost defective it will become absolete.