At this point a lot of the damage is done because even you come up with "killer game idea" it's going to take 18-24 months for said idea to become a playable reality, so Iwata and company really dropped the ball in their planning of the Wii U back in 2011 or so.
That said, what can they do at this point?
- Aggressively try to cut costs as much as possible. Push the tablet idea through till Mario Kart 8's release. If the console is still missing sales targets, then I think you gotta consider cutting your loses and making a SKU available for as cheap as possible ($199.99?) without the game pad. Sorry but you can't piss away an entire console generation because you were married to an idea that just didn't cause any excitement with general consumers.
- I would double down on celebrity endorsements and stop marketing so heavily to kids. It's a turn off to adults. Hire Megan Fox or some other B-tier, but good looking celeb to be the face of a new marketing campaign.
- Go grab Reggie and NOA, tell them to go scour for the 10 most interesting looking indie projects they can find. Finance those 10 projects. Maybe you can find the next Minecraft or Angry Birds, worst case scenario is your console just got a bunch of interesting/fresh new games to play in between all the Mario releases. And funding indie games doesn't cost a ton of money.
- Redesign the system for 2014. Shrink the GPU to 28nm and give the console and game pad a sleeker new look. Use a higher quality screen display too. Expand the remote control functionality of the tablet.
- Swing for the fences with a third party collab. I'm talking Nintendo x Final Fantasy or Zelda x Dragon Quest or Pokemon x Metal Gear Solid (ok, err, maybe not that one). Whatever. And get into development as soon as humanly possible.
- Go grab a movie license. The James Bond game rights are available. Marvel/Disney would probably be open to letting Nintendo make Avengers/Marvel Universe games like the Star Wars deal in 1990s. Nintendo may simply not have the time to create a big new IP this console cycle anymore, Bond sells well on Nintendo platforms and a high quality Marvel game would sell well on both Wii U and 3DS platforms. Both bring in slightly new/different audiences too.
- Finance the revival of some defunct third party IP. Contra and Megaman and Ghouls N' Ghosts and Shenmue ahoy.
