I can't really think of much they can do other than making the gamepad a seperate accessory.
The WiiU has basically sealed its fate regarding 3rd party support. And the vast majority of the original Wii audience that wouldn't have cared about that have moved on. So the only people left that are buying the WiiU are hardcore nintendo fans.
The WiiU needs to get cheap enough that people who might not be diehard nintendo fans will buy it as their second console for the Nintendo games. The console needs to get as inexpensive as the gamecube did, $100. And I don't see that ever happening if they don't make the gamepad an optional accessory.
Honestly the gamepad just didn't attract a wide audience like motion controls did. And heck developers themselves have hardly done any immaginitive things with the extra screen. For the most part it's just Remote Play and a menu screen. Only 10% of Vita/PS4 players use remote play for heavens sake. It is pretty clear they are just throwing away potential sales by forcing people to pay a premium because a gamepad has to be included.