If you don't need the *physical* keys to change (and well, a keycap puller and maybe spare keys would fix that), you could get a remappable mechanical keyboard.

I've got an oldschool razer blackwidow - now sold as the [blackwidow classic][1] but many keyboards of this sort would have similar features.

 - has proper switches.
 - cause of this, you can just pull and move most keys around
 - you can *buy* replacement keycaps, even as a set.
 - backlight optional, there's models without it.
 - You won't be a membrane key using plebian.  
 - You can disable, enable and remap keys to your heart's content
 - You arn't spending several thousand dollars for reconfiguring a keyboard. My key puller cost *three dollars*.



  [1]: http://www.razerzone.com/store/razer-blackwidow-ultimate-classic