Wheter you like it or not, 3rd party is a fundamental aspect on a console. The more laching 3rd party is, the more consumers will ignore that console and the more pressure 1st party has to compensate. Of all three majormanufacturers, Nintendo is the one with the most problems on this regard. They have manage to compensate this problem thanks to their strong 1st party lineup. However, with the developingtime and costs rising, Nintendo really needs to find a way to expand the software input on their consoles. Nintendo will have to try two things: One is getting more studios and companies to develope games, and the other is to make big 3rd party studios to develop for their consoles.
Nintendo needs to get more developers to work on their consoles. Keep in mind, I don't think every company will even try on this regard: the big western publishers (EA, Activision, Ubisoft, T2...) won't really care for Nintendo systems unless they know their games can sell at least one million units per game on Nintendo systems. Even if they made a profit, franchises like CoD, Fifa and Assassins Creed have abandoned the WiiU to never return, just because the sales didn't match their expectations. Blockbusters like GTA don't really care for Nintendo systems becase the sales are good enough elsewhere, and also are afraid of Nintendo's reputation as a "kiddy company". And with the rise of mobile, they have abandoned the little interest they had for handheld developement. Only a couple of franchises keep their interest on Nintendo: Lego, Just Dance, Skylanders, Disney Infinity... and even though they sell well, they definitively can't move hardware.
If Nintendo wants support for their franchises, they'll need to talk mostly to two different groups.
-Eastern publishers. Companies like Sega, Capcom, SE, Konami, Namco-Bndai, Tecmo-Koei, Marvelous... have supported Nintendo's handheld systems for a very long time. And even if they have moved a big chunk of their resources to mobile, they really never fully abandoned the handheld space. With home consoles, however, is another story. But if Nintendo wants 3rd party titles for their next home console, they have to start from here. Offering help on localising some of their titles, helping on the porting process, partially funding some exclusives, proposing crossovers and letting them use some of Nintendo's IPs... If publishers can see their games working as well as Hyrule Warriors, they might try putting their own franchises on the console.
-Smaller developers. There are a ot of small and medium developers with really good project, but lack the resources to fully reallising their ideas. Nintendo could help them a lot on that regard: by funding, advertising, localising and publishing their games, Nintendo could get a really unique library. Indie titles like Fast Racing Neo and Shantae 1/2 Hero could really use a retail release and a ton more advertisement. Also, by helping on the funding and developement of titles like Devil's Third, other 3rd parties might approach Nintendo too. Nintendo could also pay attention to the Kickstarter scene, and talk with the developers to get their games on Nintendo platforms, even if they have to partially fund it: pay attention to Sony on that regard.
I don't think this is the main problem of Nintendo. Nintendo consoles sell because of Nintendo games, this has been true since the NES. However, with their competition getting more and more games, their libraries look more appealing than Nintendo's just by sheer quantity. Also, designing and advertising their hardware properly is a must. Nintendo is used to make profits on systems that sell way less than their competition, so reaching 30-40m on their next home console could be considered a success (with their handheld helping, of couse, Nintendo would like to preserve their handheld numbers to more than 40m units sold).
Now, with all that said, 3rd parties have one big problem on Nintendo's home consoles. With consoles with small userbases like the N64, the GC and the WiiU, their games don't sell as well. Whether if this is because of lack of advertisement, inferior versions, lack of interest from the Nintendo userbase, wroing choice of genres... it's a whole different debate. Not every game costs the same to make, but publishers like to see their titles selling well (duh).
I think a good choice of IPs could help Nintendo. There's a lot of old school franchises that have had their best titles on Nintendo, and could have a good impact on hardware sales. Which franchises could help Nintendo move hardware?
