Here's how I can see it.
Relaunch.
It worked for the PS3, sort of happened and worked with the 3DS.
Redo the logo, emphasise the U part of the Wii U, perhaps remove Wii altogether and call it the Nintendo U.
New model of console. Cheaper parts so they can sell at a lower cost.
2 SKUs GamePadless with Wiimote Plus and/or Pro Controller: ~$199.99. OS defaults to the screen on TV being what is on the GamePad as default so WaraWara Plaza can't be accessed. Can't switch unless you sync a GamePad.
With GamePad & Wiimote Plus: ~$249.99.
GamePad on sale on its own $79.99
[*]As most games offer alternatives in control, you can throw a "Better with the GamePad" style thing on the box. For ones that require it, like games that require Kinect, marked clearly on the box.
[*]Bundle could include Super Mario 3D World or Mario Kart 8 to further push it
Iwata mentioned today that they're funnelling even more money into advertising and that is another reason why projected profits are lower. Use that for a massive relaunch.
Software is fine, though they need more of it, sure. Third party support is a lost cause, what Nintendo need to do is try and lure them back for the next console, but have to ride the Wii U through until 2016 at least. In the meantime, continue with the deals made with Sega, Platinum, Koei Temco etc. to make exclusives, with Nintendo fronting much of the costs.
This is the only thing I can see Nintendo do to potentially turn it around.