There's not even some gimicky catch to it; it's just a closed door! Nintendo needs to keep all peripherals running (or at least most). Since we can't use gamecube controllers on the Wii U, there should at least be some sort of support to trick the Wii software into thinking it's a Gamecube controller; Or some universal controller software to just asign buttons for any specific controller the games require! (like if i was supposed to use a sideways wii remote but could asign the d-pad and a+b on another remote, ect.)
RABBLE RABBLE RABBLE