Quick reply...
What about a device supporting all four orientations (two portraits and two landscapes)?
Not simply display supporting all four orientations, but also slide-out keyboard supporting all four orientations.
The keyboard would have to change size of buttons and their labels, so it would most likely have to be touchscreen...

Attached: schematic how a four-orientations capable slide-out keyboard could be attached to device (blue rails, black stops, green attaching clips move in the rails until they reach a stop).