I'm tempted to say some Japanese studio, but Nintendo already has a strong enough Japanese prescence. They need some Western studios. Maybe if Michel Ancel really quits Ubisoft, Nintendo could create a studio around him.

platinum games

Not a bad idea, I totaly forgot that Ancel was considering leaving Ubi.

I would rather them hire new people and expand honestly. Retro should hire a bunch of new people so they can release games more often. Apparently, they did buy a few people but not enough IMO. They need to expand all of their teams. They are already beginning to do this and the merging of console & HH teams was smart.

Quantic Dreams

Retro just moved into a much larger building. I think they need to expand their teams, but that ain't enough, they need new dev's too. 

And lol at the bolded part ^^

I wonder what sort of games Ancel would make. He's worked on 2D platformers, 3D platformers, Action Adventures, and Party games. Maybe Nintendo would let him create a new mascot. Alternatively, they could give him a minor to moderate sized IP like Donkey Kong or Kirby and say "Do as you wish with this."

The only problem is, the resulting game would likely not be radically different from Nintendo's current offerings, at least superficially.

They need another western studio like Retro.

I'd say if Ancel really is quitting, fund his studio.
Maybe he'll be nice and make a couple of exclusives.

EDIT: Bah Ninja'd

If nintendo starts up a western studio, I would like them to make a game like skyrim, unless retro's already doing that. But I'm not sure that Ancel would be the right guy for that.

Nintendo could really use another RPG maker to dedicate for their consoles and make them more appealing. Mistwalker would be an interesting choice. Platinum not so much so, to be honest their games aren't very good.

There's no way they could afford to buy huge corporations like Square Enix or Sega at this point though. Even if they had the means, the costs incurred over the next several years would be tremendous and the stock would plummet. Nintendo is in a precarious enough financial situation as it is. Maybe if Square Enix continues its downward spiral they could buy some of their assets.

Rather than buy another studio, Nintendo could hire more internal development groups focused on new innovation instead. Give them more freedom to develop apart from the traditional Nintendo style. I think this would be a much better idea.