It still goes back to the size limitations; you're only working with 8" to maybe 10" across to put a frame assembly in so at most you'll have 6"-8" side to side opening on the inside; pretty much a porthole. And every sunroof/moonroof/skylight has to have a frame around it to hold the seal and the mechanical. Plus you can bend (form it actually) glass to have a curve, but you can't really form it like a ball (front to rear + side to side) Oh you can; but the cost would skyrocket. Look at any sunroof and they're flat front to rear; curved side to side. It might have a small (very small) arc front to rear, but not as much as the Elio roofline.
We picture things in our minds and see it one way; but when it comes time to cut that hole, the reality of proportion comes into play.
Take a piece of paper; fold it in half (so it's 8.5" X 5.5") go out to your car, and hold that up over your head, and you can get a real concept of what it would really be like.
When you sat in the Elio (guessing that you did somewhere along the line) did you even notice the headliner in the Elio?
There is so much glass close to either side of your head (side windows) that you probably didn't even pay attention to it.
And look at the frame pictures; look at the available space there is to work with between the fame of the vehicle.
One last thing, factory sunroofs/moonroofs are very different from roofs you can install after the vehicle is built.
