I like ALOT of your ideas; but I'd walk a tightrope of 'immature/inappropriate' and aim Kid Icarus at 16 year olds. Pit as an innocent pervert is fun. 

How about working with Disney and Activision to get Amiibos working on Nintendo versions of Skylanders and Infinity?

I definitely think Nintendo should be working some sort of deal with Disney.

I've never played Kid Icarus (outside of failing spectacularly at the NES verison on VC), so I was guessing at the tone.

I still think it should be aiming at the tween demographic, as they're the segment that Nintendo needs to be getting onto their consoles and into their brands: if a 13 year buys a Wii U/DS for Kid Icarus then as they mature they'll be able to pick up Star Fox, Pokemon, Zelda, Mario etc etc etc, whereas if it was a 16 year old, they'd probably skip the 'younger' IP.

That said though, you can still aim a cartoon at multiple demographics, as long as the content isn't too graphic. Something like the Regular Show for instance, or the Aquabats Super Show, or Teen Titans; they hit the right side of the line in terms of being suitable for a younger audience, although there's enough there to appeal to the older kids as well.

Pikmin should go on NEW3DS!

I say it a lot but make a Pokemon game for Nintendo's home console, use DLC to constantly add new sections and creatures to the game world.

I'd basically have Nintendo developers make a version of those games exclusive for each Nintendo games device/ console.

If I had unlimited marketing funds then I'd do a major Nintendo Direct, but instead of making it just for the internet, I'd put it on a major National TV channel, with exciting, but Spoiler Free sections of the games shown. This direct would be aired on TV around the time of major games conventions, when games are ready to be properly unveiled.

Maybe a Nintendo TV show, here in the UK we have Click which is a BBC News Program centered around Technology, it does show off games consoles. Something like that, but for Nintendo games, shown in a 30 minute segment a few times a year, shown on a major TV Channel, at a time of the day when the target audience for those games are home.

As others have said make Movies and TV Shows, along with good trailers for those games. Have an E3 presence like Microsoft and Sony every year.

Maybe E3 and other games conferences could be broadcast on national TV. Perhaps the likes of IGN and other gaming media could have a TV Channel for showing off games, with reviews, news, previews and general marketing for games and Nintendo could have their presence on that channel.

Get those games properly advertized, put a good amount of focus onto the main characters of those games, give them an identy that people relate too and show those attributes off to the world.

As far as game design goes, listen to the fans, put what they want into the games, provided it of course works, but actually give the fans what they want and actually make games for those particularly franchises that are less well known, because those games aren't going to become mainstream if you don't even have a go at making those products.