They did Hyrule Warriors which seemed moderately successful and I don't think that hardcore Zelda fans consider the series tarnished or anything like that despite being a vast departure from Zelda games...

Why not try a Metroid Halo-like spinoff? I know Metroid Prime has been a successful FPS and personally if I would be happy enough if I heard they were making multiplayer similar to Prime Hunters for the Wii U, but a Metroid Prime sequel would not really occupy the same niche as the "military shooters" the OP alludes to, unless it had a major change in ethos (which in turn would piss off existing Metroid fans). But aim the game clearly as a spinoff (or even crossover? "Metroid Of Honour"?) and it could be designed to appeal more to the COD tastes (without being a complete rip off) without betraying the franchise. This would work especially well if they also made a traditional / mainline Metroid game (the same way Hyrule Warriors did not replace Zelda U), and it would even free up options to focus on different elements (platformer, exploration, action adventure, whatever) that the series is known for without worrying too much about filling the FPS niche.

Of course I realise that is a pipe dream, and even if it wasn't it may not actually make business sense since the Metroid brand might actually reduce sales compared to a similar shooter that's a new IP (since Metroid is not a huge selling franchise). But it's interesting to think about the different possibilities.

With what exactly did you disagree?  We're pretty much on the same boat when it comes to this topic. 

By the way, why do you think Nintendo's next console will happen in 2016? I mean, the only way I can see Ninty doing what you're suggesting is if this gen is as long as the last one, or at the very least 7 years long.

They sold Rare because they where somewhat forced to.
Nintendo had a minority in Rare and the Stamper brothers then sold the majority to MS. Selling the rest was the best they could make of a bad situation.

As for fps in general, Nintendo could need a wider audience. Right now they seem to havee Nintendofans and families, that actually care wha their kids play.

Stuff like Bayonetta, Xenoblade and Devils Third is kind of a first step. But they will need western games of different types as well.
That doesn't need to harm the traditional Nintendo games. And Nintendo could as well be doing things a little different with mature games.

It definitely doesn't need to be 'military' though. There has been far to much military stuff over the last years and people are getting bored of that.
But a new fps ip would have to be just one step. There's more than that what is needed to really widen the audience. At the same time Nintendo has to keep their traditional ip's up and running. There's need for a good mixture.

And i really think they have to start it now with Wii U and then really get it going on the next console.

I doubt Nintendo itself could make a good FPS game, but if they get a good developer to do it I say why not. But I would only be interested if its more like Battlefield than COD.

They should have taken their opportunities when they had the chance.
http://www.geek.com/games/timesplitters-4-never-came-to-be-1530102/

No, we have enough shooters already. Nintendo should make games that are completely unique, games you can only find on Nintendo platforms. If they start to copy successful games, they lose their last bit of raison d'être.

Just Dance...

Sure, why not? But unless they have the best version of CoD, or Battlefield or perhaps now Destiny, then it's just ticking a box. It's not going to suddenly turn military multiplayer fans into Nintendo fans.

moms are okay, they play silently their games, they harm noone, and maybe they start real gaming when they are tired of sport and wanna play something with the kids...

You never bought a wii? XD