Probably not in the right thread... but how about this crazy idea: Instead of having a physical HW-keyboard in slide out tray, what if there is another touch screen? The function of this second screen is to be the virtual keyboard, as well as secondary function as a touchpad to replace the mouse (as seen in laptops). The function of the screen between keyboard/touchpad maybe can be accomplished with a single mode button somewhere...

The secondary screen does not need to be very high resolution, something like 320x120 might be enough... it can be even black&white!. If this (the mouse part) works well then the main screen would not even need to be touch screen!

Now... waiting for your comments about how crazy I'm when suggesting this...