Larger sensor than 24x36 would be nice.

A nice round sensor optimized for the diameter of DSLR cameras. Sounds stupid, but if you could choose your crop within the menu it would be pretty cool.

For example, standard 24x36 in landscape vs 24x36 in portrait without tilting the camera. But now you want a standard square format, just choose it from the menu. And if you want the full size, select the circle. Maybe you want to optimize for 8x10s or 5x7s... Now you have options.

Why does the sensor "have to be" a rectangle? Working with current mounts, you should be able to change the shape of the sensor. There should be no need to change the lenses so long as you stay within the visible range of the lens. 24x36 is just everyone thinking inside the box.

A 43mm circle sensor, based on the D800, would have a 60.96mp output.